i don't know who started the egg using trend, but i guess it was probably stone age chef making his unleavened spelt breakfast pancakes over an open fire or something similar. i doubt he had any baking powder- which was in existance, but not widely used till the 1800's- i guess people have always just used eggs in baked goods, cos when they developed the reciepes in the really olden olden days, lol, they had loads of eggs to hand, but probably no baking powder .... or ground flax seeds, bananas or silken tofu (at least in most parts of the world).
about replacing them automatically- i think a lot of that is grounded in the theory that people tend to do what they've always done. if they grew up cooking with eggs in stuff, and they see 'egg replacer' in the grocery store, they think they need to use it to replace the egg in their vegan cookery 'willy nilly' (that's a colloquial english phrase, i hope its not misconstrewed, hahaha) cos that egg  must have been there for an important secret cookery reason that they don't know (like i do) lol.
i've only just realised a little while ago that when i make pancakes etc i'm really just doubling up if i use that powdered egg replacer to replace my eggs, and then use baking powder to make the pancakes rise, and i still tend to add the egg replacer on reflex. (perhaps i'm not very smart as far as cooking goes- it took me ages to realise that it was a bit pointless, and i still do it.)
but thanks for the informative vent, lol, it's clarified in my head that i maybe don't need to always reach for my egg replacer if i'm using baking powder at the same time.