Seems some people fully expect to pay for their own meal when invited to restaurant birthday party and some think it's tacky. Around here it's the norm that each person pays for themselves. An invitation would go out stating the restaurant and time and say something like cake will be provided. everyone expects to pay for their own meal. I have both been to these, and given these, it's the norm. I would be shocked if the host offered to pay for everyone!
People in different economic circumstances also do things differently.
It's very easy for a person to proclaim that they took 90 people to Tavern on the Green and had a Fahhhhbulous time celebrating their spouses birthday while calling anything that anyone else does "tacky."
Many people with different income levels would never in a million years even assume that one of their friends is going to pick up the tab for 6 - 8 - or 10 people getting together at a restaurant to celebrate someone's birthday. They all pay their own way, this is just what's 'done.'
Are these the people that you, (general you), wish to call "tacky?"
I would guess that Emily Post would have a far harsher word than 'tacky' to describe people who would call others derogatory terms in this situation.
Etiquette schmetiquette.