It's something that the wrestling business borrowed from boxing because the ten count finish is something that they've done in boxing and everybody is aware of it. The only way to avoid losing is to get up before the count of ten.
Weapons are allowed and wrestlers able to brawl all over the arena. There are no pinfalls, submissions, countouts or disqualifications. It can only end when a wrestler is unable to answer a ten count after being downed.
A Last Man Standing Match is one of the most physical kinds of matches that can take place at a WWE event.