Indeed, as someone who is Indian but not vegan or vegetarian, my meals during the weekdays are meatfree and usually vegan as well. This is not by conscious choice, the recipes are simply made that way. I suppose back in the day where meat was expensive, as you mentioned, so people made vegetable based meals and that's what stuck. During the weekends with family gathered, people eat meat, just as I do too on weekends. It becomes a sort of mini feast every weekend.

In the US, it often puzzles me to hear that some people actually don't consider a meatless meal a meal at all, as if they have to eat meat for all three meals of the day. That is unknown to Indians, generally speaking.