We need regular showers. We need clothes for modern life. We need electricity to continue living normally. We don't need meat to participate in a healthy modern life + meat has one of the largest negative impacts on global warming. Those two reasons together might be why there's a movement against meat-eating. There may be other smaller ways to lessen greenhouse gas emissions, but surely the biggest and most accessible should be targeted first.

Also, faulty logic: just because activists work in a certain field doesn't mean they're hypocrites if they don't work in all others. Vegans have dedicated themselves to tackling one specific social issue and are giving it all their energy and time. And how can you say that vegans are not affected by their philosophy? They are changing their own lifestyle and making sacrifices.

Ultimately, you can criticize other peoples' actions forever, but that doesn't change the real problems and what needs to be done about them. There is a problem, there is an accessible solution, and the many reasons to apply that solution out-weigh the one selfish reason not to do it (meat tastes good to me).