There are massive efforts to sell more dairy/beef in general. The governments in the USA and other countries subsidize it at massive scales. Other proteins are just fine, but there’s no pea protein lobby. Well, certainly not at the same scale.

The economics for cheaper proteins are actually incredible, too. The incentives simply don’t exist in the right places to facilitate the right legislation and public awareness, though. Many of us grew up with “Got Milk?” and “Beef is What’s for Dinner”, not “Got Lentils?”. It really made a difference.

Whey is the best if you don't have any dairy allergies and your body handles it well.

It mixes better, tastes more neutral, and generally has more leucine than those other options, which is important for signalling muscle synthesis

I've never encountered a soy or pea protein that didn't make flavor noticeably worse. Whey protein isolate can be made essentially flavor neutral.

There are higher heavy metal levels in non dairy based protein supplements.

Why do government cheese when you can do government gainz