They do come with a manual. (Says the guy who has never read his dishwasher’s manual.)
Houses typically include the appliances, so unless you buy from one of those rare boomer types that filed everything away, you probably don’t have it. I guess you could search it online, now I’m typing this out…
Or maybe you buy a house and later renovate the kitchen, adding in a brand new dishwasher because there never was one to begin with.
Or maybe you buy a new development and it either has no kitchen appliances or furniture, or it has brand new appliances so the manuals and other documents are kept.
Lots of ways to still have the manual. Where I live, the cost of a new development is maybe 20-30% more per unit of area than a condo in a 40-60 year old commie block, but they look way nicer inside and out and they keep heat way better, which is important when you get really damn cold winters. Plus you can get better loan terms if it’s certified C energy class or above usually. For some banks it has to be A. Downside is you have to wait while they build the damn thing.
Or maybe like me, buy a house that had a dishwasher, pull it out and throw it away because you’re a single man.
Get married wife wants a dishwasher, buy a new one go looking for the manual one day and find the original dishwasher manual in the boomer folder of things left behind by the previous owner