https://screenrant.com/why-cheers-ended-canceled-explained/

Cheers had a successful run on NBC that ended in one of the most-watched series finales of all time, but it ended for one major reason.

"This potentially could have saved Cheers from producing an overdone and uninspired twelfth season which could have tarnished its legacy"

I fully agree with this. Supernatural (created for 5 seasons) should have ended with season 11 (great season) but they went on and on. Season 12 was bad and it just got worst season after season. I can't talk about the show without saying this so it indeed tarnished its legacy.

Cheers ended because the state revoked their liquor license. Nobody goes to the bar to drink root beer.

I heard that Woody was going to take over as the protagonist had the show continued after Season 11. But Woody Harrelson didn't want to continue without Ted Danson, which was probably the best choice, to be honest.