I've also rapidly seen the number of popular vegan restaurants explode in the city of Toronto, where I live, over the past 3-4 years.
One note a few people are making is that you don't have to be vegan to eat vegan. This is true, and purposeful - vegan food is generally of a relatively high quality - and a lot of what it offers is the direct contrast to most other North American-favoured food.
Like they say Lucky Charms are a 'part of a balanced breakfast', followed by a picture of a table with orange juice, a banana, etc...so it is that, if I have a busy work day, and we order some greasy pizza in, I can go hit he Freshii on my way out and balance out the sausage, grease, and cheese that way.
I think more and more people are simply realizing just how unhealthy our diet is, here in North America, and as these potions become more available, and awareness of them is increasing, I think all this indicates is expected are finally waking up from a sense of brainwashing that's gone on in advertising everywhere, getting us to honestly shove the worst things in our bodies over the past few decades.
There are environmental concerns with Vegan food, particularly in transit of the more obscure and in demand things like Avacados - so I do get a giggle when people are all uppity about how ethical they're being - but obviously there are ethical and environmental concerns with the treatment of animals, as well.
Overall, it's no surprise to see this data, I'd argue in-restaurant demand, at least in this city, has similarly exploded.
It's good. It means we are collectively eating a little better, and that's something that affects both the mind and the body.