Because what do you think matters more in an online game:

A. Smooth and consistent client experience, where bullets hit what you aim at (client-side prediction) where aimbots and wallhacks work.

B. Jittery/laggy client experience, where aimbots still work, but wallhacks are disabled?

You can only choose one option.

Generally, everyone agrees "A" is the best option and cheaters will be dealt with at game time. It's annoying, but that's the cost of online video games.

The many tradeoffs involved are not trivial, this can only feasibly work well on LAN.

This is the reason why Valorant is the least playable among all competitive shooters if your internet is anything lesser than Google campus fiber, ironically in spite of having even-slower-than-CS movement physics on its side to mask the problem.

Riot conveniently cherry picks the best case scenario and handwaves the actual technical tradeoffs in their smug "we solved peeker's advantage!" engineering blog posts that are really just barely-disguised monorail Gish gallop.

CSGO already added this over a decade ago.