Boxing in real life is not like boxing in movies. No fighter can go 12 rounds just throwing hands all the time. The clinch is used often for strategic purposes, to stop the momentum or interrupt the rhythm of the other fighter. It also is used to get some kind of rest when one is getting pummelled and can't find a way out.
Sometimes it's abused of course. But it is very much a part of the sport.
But then you would have knock outs happen in under a minute. That would provide less value for the people who spent money to either watch the fight or be there in person. I think it's structured in 12 rounds so that the viewers can betterbbe entertained, even though I feel like that doesn't really show who's the better fighter, rather who can hold out the longest.
Why would more protective padding lead to more knockouts?
I'd propose that with better head protection, you could have three, four-round fights in the same time span as a twelve-round fight, with more guaranteed boxing.