I'm wondering what the mentality is behind this?
I read that there is a divide between the 1/2e era and 3/4e era DMs and players. This isn't a universal, but-
The earlier ear tends to have those who are less encumbered by the RAW, viewing them more as guidelines, and more open to employing non-standard materials to supplement the game (and tweak as necessary). See also, Dragon magazine "NPC" classes and races.
The later era had more options available, and there was thus the (occasional?) need to strictly limit what came into the game; new options could easily unbalance the game.
Obviously, this doesn't apply to everyone. I was just curious if others had notice it.