I don't think many people are saying that they would miss meat.
I think lots of people would find it harder not to have any milk products, including milk in coffee, cheese, etc. A vegetarian meal would be fine and probably unnoticeable - it's the replacements for dairy that I often find are the worst.
I wouldn't claim allergy to soya as it's just an intolerance, wouldn't normally even have mentioned it, as I only react if there is enough, and I wouldn't normally expect a wedding to have that much in it. But if I didn't know, and it turned out there was soya milk or other substitutes for a number of ingredients, I would be quite ill.
So it's not really about the lack of meat. It's about some of the replacements for certain products, that many vegans would think are fine, but others might not - and might not know they are problems until they have enough of them. I didn't know about soya until I had to go dairy-free for a while to test for allergies, and only then did I have a problem as it was in enough of those foods to cause an issue. Since then, I don't encounter it often enough for it to matter.
So not telling people that it's vegan, but then having food with lots of soya stuff in, could well result in issues.
Same with lentils, etc or other fibrous foods.