This is not automatic, it is a choice the seller and their agent make when the listing goes up. A seller who reduces or removes the offer to the buyer's side can shrink the pool of agents actively bringing buyers to the home, which is a real tradeoff against whatever is saved.
Buyers now more commonly sign a written agreement with their own agent before touring homes, so the buyer's side of the commission conversation is more explicit than it used to be, but that shift changes disclosure, not whether a seller is still allowed to offer to pay it.
Whether offering that commission helps or costs you depends on your specific price point and competition. Get your hand-reviewed valuation from Joel Dyck.