>>51412280In my personal headcannon, evolutions are actually the Pokémons natural maturity. It is actually the human intervention that makes them evolve prematurely by special items or overtraining, refuse to evolve or breed at their first stages of growth.
Nidoqueen being unable is indeed a design choice, but only because they messed her up in gen 2 and insread of aknowledge It and fix her, they just decided to make It a "feature".
