Interestingly,well for me anyway,is that despite the unassailable difficulties which beset the poor caterer, there are some that manage.
In terms of dining out, I think it is fair to say that more often than not, we're talking ubiquitous chains, such as Wetherspoons, Harvester, Brewer's Fayre et al. Before I was vegan, the default venue for Aunty Maud's birthday would be the local Harvester, not a vast vegetarian choice but you could get something. When I became vegan seven years ago, the Harvester was no longer viable, due to their sod all for vegans policy. I realise that my family ditching them won't exactly cause the share price to collapse, but every little helps.
Nowadays if I find myself being frogmarched to some dire family gathering, we end up at the Toby Carvery. Admittedly it's like walking onto the set of 'Silent Witness' with different species substituted for the human cadavers, but they do offer two vegan main courses. No starters or desserts yet but it's a start.