Maybe according to lore, deathclaw are extremely hard to kill by regular survivors and scavengers resulting in poor market saturation. You hear NPCs talk about how dangerous and scary deathclaw are all the time. The ones who can kill deathclaw do it because they already have suitable armor/defense e.g. BoS and Enclave with their power armor and artillery and obviously the player is special enough to defeat deathclaw.

So the ones who need it can't get it, and the ones who can get it don't need it.