1 Dwalin: Oor last night in thu Badlands o' Skroong. I’m a but surprased we ha’n’t bin attacked by bundits.
2 Lambert: What would you do if we were?
2 Dwalin: Ah’d slit their throots und take their goold!
3 {beat}
4 Lambert: We’re the bandits!
4 Kyros: Oh, you realised?

Some roleplaying campaigns descend into a state where the PCs aren't virtuous heroes, but rather simply go around killing and looting everything they can. If everyone involved in the game is on board for this, then sure, have fun any way you like.

But often it isn't fun for everyone. The GM in particular can easily get sick of this sort of thing from players, when they had an expectation of running a setting for the heroes to be... well... heroes in. And if not all the players are of one mind, it rapidly gets annoying for the ones trying to do good in the campaign world.

Players who insist on trying to kill and loot everything are called murder hobos. There are ways to deal with such problem players in a game where others want a less murdery experience. Unfortunately, a lot of the advice you can find online is bad. Literally the first hit I got when I searched for "murder hobo" is this article from Screenrant, which says:

The best way to handle a Murder Hobo in a Dungeons & Dragons party is to enact consequences for extreme actions. If a player is running through a town destroying shops and killing the shopkeepers to take what they want, the Dungeon Master could have the town put a bounty on the player's head. If the player kills an NPC instead of interacting with them to get a key item or information, it could be that information is permanently lost to the party. By putting weight behind player actions, it gives more incentive to think before they act - especially if the D&D party starts to get frustrated at not being able to finish quests, or lose their ability to go into towns to purchase potions and weapons.

Wrong. Flat out wrong.

The best way to deal with a murder hobo is NOT to enact in-game consequences. The best way is to talk to the player out of the game, tell them that their playing style is annoying and ruining everyone else's fun, and they can either change their behaviour or find some other gaming group to play with.

Never deal with a problem gamer with in-game actions. Doing stuff in-game doesn't address the actual problem, which is that the player is being a jerk. Talk to them as a person, not as a game character.

Sorry for the rant, but there's so much bad advice about this problem on the net.