Are you actually listening to what people are saying? They may have all those things you list in their house, but for people who do not limit our diet in any way, you will find that most of the dishes we cook do have at least eggs or dairy. We do not enlessly scan the list of ingredients in every food in the house to rule out the ones we "cannot" eat, because we eat everything. Catering for a vegan is a massive inconvenience which completely changes the way we can cook, it is not only about makling sure there is no meat in it. You have to check the ingredients of every bloody thing in the cupboard. My vegetable stock is actually not vegan. My cooking wine is not vegan. If you have spent years cooking that way and learning about every single ingredient in your pantry, then you're used to it and it's no extra effort for you. However it is not the same for everyone.
Yes, catering for specific eating needs is a pain in the arse. I will do it for good friends, but I resent having to do it for a generic meal or get-together. In the last one I had only one person who was gluten-intolerant in a group of 12. I had to purchase special flour for the baking and gluten-free pasta for the meal which cost a fortune and which I have never ever used since, so had to end up throwing the rest away, as I did not like the taste as much as the gluten-full versions. I found out last minute that soy sauce was not gluten free (I am sure this is well known for gluten-intolerant people, but as I never have to worry about it I had not even thought about it) and had to dash to the supermarket to get a glute-free one, more expensive and which has remained unused ever since. The stress about having made a mistake and potentially causing harm is massive.
It can be done, but it is a massive inconvenience. I am certainly not offering to host again.
And you can repeat till you're red in the face about how delicious vegan food "can" be, but the reality is that most vegan food provided by catering services is absolute shit and no one eats it. One thing is how the world "should" or "could" be and a very different one how it actually is. The only people who appear to enjoy vegan food are vegans.