I mean, when I roll a character’s ability scores, I stick with the results I rolled. But, when I’m DMing I allow re-rolls because, like I said, I want my players to be happy with the characters they’re playing. Some players (let’s be honest, a lot of players), will not be happy with a character who has below average stats, and may not even be happy with a character who has average stats. And the last thing I want is a player to have a bad time because they chose to roll randomly but got immediate buyer’s remorse when they got middling results.