knights were the ones that participated in medieval tournaments.
jousts
Tournaments
Knights participated in tournaments, which were often jousting competitions or melees where they showcased their skills in combat and horsemanship. Tournaments were important events for knights to gain fame, honor, and prestige in medieval society.
Knights participated in mock battles known as jousting tournaments. These tournaments were popular in the Middle Ages and served as a way for knights to showcase their combat skills and prowess. Jousting tournaments were also a form of entertainment for nobles and commoners alike.
whenever they wanted to
There are tournaments held for gamers. Most of these tournaments are held online and can be multi-player or single player. One does compete for monetary prizes.
knights took part in tournaments such as jousting and wooing ladies in their time off
Did they practice fighting? Yes. They trained as soldiers, and would compete with one another.
because its not cool
Knights did not won their armors in tournaments, they bought them, maybe with the gold won in tournament.
Usually, Halo tournaments are held within your community, but if you check Bungie.net, they do occasionally advertise tournaments.