I have an uncountable amount of poison in my inventory.
I never end up using it, as it takes all of your combat action(s) to do so.
My lvl10 2-handed Pally can attack 3 times per turn for 100+ damage with smites. Yet if I decide to apply basic poison to his axe (+1d4 damage), he has give all of those attacks up, which makes no sense.
Wouldn't it be better to set poison as a bonus action?
P.S. I realize you can apply it before battle starts, but that's not always possible/easy to forget.