I don't understand commercial aspect of large OSS like package managers but i was wondering for years why this was missing from npm. I think typosquatting was handled by npm last year but only after some popular miss typed packages started stealing developer creds.
The people building package managers are unaware of these problems going into it and it becomes extremely disruptive to start adding these things later on since your entire ecosystem is built on the assumption that they can do these things.
It's also shockingly controversial to suggest typosquatting suggestions. I made this suggestion ages ago for cargo, demonstrated that basic distance checks would have impacted <1% of crates over all time, and people still didn't want it.