Personally, I buy protein powder even though I know the ingredients are actually too cheap to justify the price. But I’m too lazy, and the reward of a cold chocolate shake after working out makes me forget about the outrageous cost. It’s a little guilty pleasure I’ve come to terms with.
Because the powder is in most cases a supplement to the food and not the food itself. Having a protein drink after workout does not exclude eating a well rounded (to your needs) meal. It is complementary to it. Yeah you could chug 10 egs or so after the workout, but that isn’t that fun.