Man, as an Indian, this is hard to read. You're spreading a lot of misinformation about Indian food.
> Which is possibly also a reason why vegan food is popular in India.
First, while there are a lot of tasty Indian vegetarian dishes, vegan food is decidedly not a cultural thing. We use butter and ghee pretty commonly in food: definitely not vegan. India is the world's largest milk producer; also not vegan. That dal you refer to will often have a "tadka" of ghee and spices on top. The "dal makhani" - another popular restaurant dish - literally means "buttered dal".
And the reason pre-cooked meat pieces are added to curries in restaurants is that we need to get the food to you in 5-7 minutes. We can't cook it leisurely for 25-30 minutes in the gravy like we would do at home. It's called "mise en place" in the restaurant business.
> Lots of Indian restaurants usually have vegan or vegetarian versions of most of their curries where they toss in some tofu or paneer instead of meat.
If it's India, you're talking about, you're unlikely to find tofu being used in a restaurant. Paneer is made from milk, so...not vegan. Maybe restaurants abroad do it differently.
> And the whole point of heavy spicing in countries with warm climates like India was historically to mask the flavor of cheap cuts of meat that were maybe a bit past their prime. Which is possibly also a reason why vegan food is popular in India.
OK, this annoying canard is the worst. [1] Spices and meat used to be both historically expensive. A bit of research will tell you that. You know, that whole "spice trade" thing. Malaysian, Singaporean, Sri Lankan, food also use spices and they're not vegetarian cultures at all. (For that matter, only some 30% of Indians are vegetarians, despite the stereotype, but that's a discussion for another day.)
TL;DR India has lots of good vegetarian food, but hardly any of us are vegans.
[1] https://en.wikipedia.org/wiki/Spice#Preservative_claim