Because complying with GMP is tedious and expensive. One mistake and you could end up with blood poisoning or a brain-eating microbe. Lab grade material is not the same as pharmaceutical grade material. You can get a lot of expensive anti-cancer drugs too at bulk prices from lab suppliers. That does not mean they are rated for human consumption. What's good for the lab rat is not necessarily good for the homo sapien.

https://en.m.wikipedia.org/wiki/Good_manufacturing_practice

Granted, more biohacking and bio experimentation is a good thing. Innovation should not be gatekept by institutions and the establishment.

Here's a startup idea for whoever's interested:

Take lab grade pharmaceutical drugs and turn them into human-rate drugs at a low cost.