> No garlic, no onions, etc.

The no garlic and no onion are part of a much broader practice to avoid root vegetables. Anything that grows below the ground is not consumed. Jains (the people who follow Jainism) mostly follow this (I say “mostly” because even though they’re supposed to, many may not).

Orthodox Hindus may also follow similar practices. Hindu festivals and rituals also avoid onion and garlic.

There’s a lot more to say than can be contained in a comment. You can read about Jain food and Sattvic food to know more.