Everywhere, everybody, says to leave the door open on your front-load laundry washer so it can dry out and not accumulate mold.
But no one, anywhere, says to leave the door open on your dishwasher.
Why is that?
(FYI: I googled the crap out of this and I also checked for more appropriate StackExchange sites....but this seems to be it.)
TL;DR Temperature
Dishwashers use hot water, because that's the way to clean dishes. Then they heat up the hot water even more to sanitize the dishes. Food safety requires it.
US dishwashers normally connect directly to the hot water supply, so for basic wash/rinse cycles no extra heating is needed. Many dishwashers in other places connect to the cold water supply and have to heat all the water.
Hand dishwashing obviously uses cooler water, but adds both more direct mechanical scrubbing (though that raises the "dirty sponge" problem) and the ability to hand inspect each item to make sure it is physically clean and then thoroughly rinsed in hot water. A dishwasher has to function in a way that makes sure everything gets fully cleaned - and extra hot water is a key to that.
Clothes washers can use hot or cold water, or a mixture. But generally, except for things like underwear, you don't use hot water most of the time because it is harder on fabric and simply not necessary.
Mold simply won't survive the dishwasher cycles. It could survive the clothes washer cycles. There are differences in the detergents and other issues. But the main thing is the heat.
Certainly washing machine door seals are more prone to mould, but there's another reason to leave the dishwasher door shut: It's perfectly placed for walking into and tripping over, in the kitchen where you're likely to be carrying things around (hot and/or sharp things at that). If you walk into a washing machine door, chances are you'll bump it out of the way. Because a dishwasher is low, small kids can easily access it if open - tempting leftovers anyone? Cutlery (even possibly sharp knives) goes in the bottom, there's a further hazard if they fiddle with that.
That said I often leave mine wide open to finish drying, with at least the bottom rack pulled out (not open just a crack under a wooden worktop, even a sealed one). I also leave it open when tidying up, and the worst that's happened is a bruise on my shin.
A dishwasher's main compartment is vented -- notice the steam vented when it hits the dry cycle. A front load clothes washer is not vented.
There isn't a lot of passive ventilation, but you will notice 12 hrs after a dishwasher has been run, you'll notice the seals are dry. A front load clothes washer's seal will continue to be wet days after it's last use.
I think most dishwashers have a pretty good dry cycle that gets the internals of the dish washing compartment up to temps that kill most bacteria, mold, or anything that would end up stinking in a closed off environment over time. Additionally, by the time you unload the hot/warm dish washer, the majority of the residual moisture in the compartment has evaporated due to the higher temperature of the water.
Conventional clothes washers on the other hand don't typically get to very hot temperature at any point in their cycle. Even though hot settings can be used for the wash cycle, no temperature is ever reached that could dry the clothes or fully dry the drum and any internals that are wet. Once the cycle is complete, the wet clothes are put in the dryer to complete the job and the washing machine is left sopping wet, likely with pooled water in the bottom most parts that contain live organisms and plenty of dead skin to live on. If you seal that off by closing the door, the water doesn't have a chance to evaporate so it turns into Primordial Soup waiting the start sentient life.
We made the switch to this large capacity washer/dryer combo several years ago and I don't think we've ever been more happy with an appliance purchase.
These all-in-one washer/dryers have been around for a while and they're very popular in Europe, but this is the only one that we've found that takes the same amount of clothes as a normal load you would do with a standard washer dryer. The all-in-ones work in a pretty similar way to dishwashers with their dry cycle. The clothes go through a normal wash and the spun well to get as much water out as possible. During the dry process, the machine heats the drum and clothes up to a pretty high temp while circulating air within the machine past a heat exchanger that condenses the humid air and pumps out the condensed water to the drain. The end result is clean clothes that are pretty warm/hot, but since the machine is vent-less, they're not "100% dry" right when you open the door. But since the moisture is warm in the clothes, it evaporates immediately upon taking the clothes out. Since the machine gets to pretty high temps during the dry cycle, I think it sanitizes everything and there's no chance of weird smells developing if the machine is left closed. We've even thrown clothes in, run a cycle so the clothes are washed and dried, we went out of town for several days, then when we get back we pulled the clothes out and they were dry and smelled super fresh.
With our all-in-one washer dryer, we always keep the door closed, and it doesn't get funky.
Edit: just saw @manassehkatz-Moving 2 Codidact's response conclusion and realized we were talking on the same line. I agree, the main difference between conventional clothes washers stinking and dishwashers not having an issue is just the difference in heat reached during their cycles.
To answer the question - the internet talks about leaving washing machines open versus dishwashers because that is a bigger issue to most people. It isn't necessarily thorough or accurate, but reflects what is of interest (because what is of interest sells ads). Bottom line is that the internet doesn't know everything. But with this stack exchange post, there are at least 2 people on the internet that say they leave their dishwashers open - so if you need internet confirmation you now have it! I have personally found that it depends on how well the dishwasher dries out during the dry cycle. I have one dishwasher that remains wet even after the dry cycle and will mold if I leave dishes in it for a few days after use. So I empty it and leave the door open after each use. So best advice - use your own good judgement to decide if you should leave your particular dishwasher open. It is probably better than the internet in this case.
