This is a bit like why computers happen to use binary and not ternary. Everything has been tried before.

There's a long and rich history for artificial neural networks but everybody seems to gravitate toward fewer moving parts in their already uncertain and difficult work.

I guess eventually the paved road of today's MLPs with GPUs became so convenient to use that very few have the time or means to try something radically different without good reason.

This is a fun read by the way: https://stats.stackexchange.com/questions/468606/why-arent-neural-networks-used-with-rbf-activation-functions-or-other-non-mono