"Historical record does support Joe here, Bareknuckle boxing was focused upon "Broughton's Mark" or other means of attritionin pursuit of the finish rather than the head. However, there are some factors which he fails to consider.
Firstly, though the hands do not have quite so comprehensive a domain as the brain, they are the fundamental tools of the average human person. Pretty much every interaction most people have with the world is done via the hands, and most any job will require some usage of manual dexterity. By eliminating the protective measures, one only exchanges one form of long-term injury for another.
Furthermore, bare-knuckles produce far greater a mangling of the flesh than do gloves. I recommend a read of Boxiana to grasp the unique tactics encouraged by the grisly wages of bareknuckle fighting. Bareknuckles draw blood easily, and with sharper, straighter shots being encouraged, it doesn't take long for a fight to become a literal, and perhaps distasteful, bloodbath. Furthermore, swelling and other forms of soft-tissue damage would see a similar rise in prominence. These factors would not be good for the sport's public perception, nor would many fighters welcome the reality of gradual facial disfigurement.
In the fight itself, instead of a quick knockout, the "punchers chance" was often expressed through the blinding of an opponent. Jack Slack, a notably powerful pugilist from whom the analyst takes his name, was known for his fight changing power, and was often accused of defeating more skilled boxers by luck. He did this, not by catching them upon the chin, but by striking with a chopping backfist between the eyes repeatedly. This would literally blind his opponents with blood and agitated tissue, allowing him to strike at them further. These fights could proceed past a potential ten or more rounds after this occurred.
On that topic, victories during this era were most often attritive, occurring over dozens of rounds, rounds which ended only upon a knockdown by throw or strike. With the lesser presence of power punching, most matches ultimately became contests of endurance.
In the modern era of pay-per-view and limited attention span (the latter being in no way new), this would make the stand-up game far less popular, and potentially alienate the many fans who only watch MMA for the Knockouts.
Ultimately, though the perspective that bareknuckle fighting is less damaging to the neurological health of the participants, I do not believe that there is a market for it, and it could easily become a sport unto itself, separate from the MMA we know today." - Kenny Florian