Boxing has evolved grudgingly over the last 150 years. There was a time when a fight continued until one man could fight no more or was knocked out. The three-minute round was introduced. The bare-knuckle era ended with the advent of gloves. Of relatively recent date is the 12 round cap on all bouts.
Some jurisdictions now have thumbless gloves to prevent eye injuries.
The longest-standing stricture in boxing is no hitting below the belt. Just imagine, however, if we were to add the injunction against punches above the shoulders. The activity would be infinitely safer and thereby cease to be boxing. It would be like playing tennis without a net. The gravamen of this grim game is, and has always been, to inflict maximum injury on your opponent and to avoid it oneself.