Medieval kings didn't like tournaments.

Medieval kings headed small, weak central governments that had only a tiny standing army. The army they used for war was the knights who spent most of their time out living their lives, heading up farms, collecting rents from tenants, getting bored.

When the knights got bored from slow rural life they were ready and eager for tournaments, play war.

The biggest, best loved events at tournaments were team conflicts that really were a lot like war. Men got killed. Men got injured. Men got maimed for life.

Kings didn't like their army out there doing each other serious injury for fun.

However, kings knew they couldn't stop tournaments. Participants and audience liked tournaments. If kings outlawed, they'd happen anyway. There were no cops, and Europe had lots of empty space.

So kings went along with tournaments because they had no choice.