And I don't really have a feel for whether more cleanliness is a benefit compared to the hormetic effect of exercising the immune system.
Could you elaborate on this? My understanding is even if you're using a sink/basin filled with soapy water this is still almost always less efficient than a dishwasher.
Do you own very few dishes or something? That's the only reason I can imagine not being able to fill it before needing to run it. Even before having a kid my wife and I could easily fill the dishwasher daily since we cook quite a bit.
I could reduce a bit the number of glasses and cups by reusing them more but anyway,the dishwasher makes a big difference.
Now that I cook for 2-3 people and more on holidays, I know from practical experience that the number of dirty dishes generated and the water used quickly exceeds anything a dishwasher would use. The use of water also increases when you cook big batches of food, so you can have quick meals available for lunches and dinners when you're too tired too cook and/or broke to go out to a restaurant/takeout.
If someone tried to take away my dishwasher, I would put their head on a pike in the front yard as a warning to anyone else who tried.
The one thing I've learned from this article and the comments here is that I really should run a load every night, even if the machine isn't totally full, because there are always more dishes used than it looks like at first glance.