Change will not happen over night. Vegans need to use their voice through money and restaurant reviews.
From my experience lot of restaurants just do not know that there is a legitimate demand for plant based meals. Often well established restaurants see no need to accommodate for vegans/vegetarians. It’s not out of malice, but out of ignorance.
Shunning restaurants when they don’t know what they’re doing wrong is a lose-lose approach.
A win-win situation would be to request vegan options, and ONLY order vegan. Often times when you only order vegan, you don’t run up the bill as much. Soon they will craft more vegan options so they can make more money.