I fear I disagree and agree with both of you. ;-) The various videos I have seen up of "bare knuckle boxing" is indeed just unsanctioned modern boxing. And I have seen footage where they were wearing regular boxing gloves and it looked like any other boxing bout. Now, this is not to say it is necessarily "good" boxing! But it is not the bare knuckle boxing of John L Sullivan's day. They are not using the techniques and methods of "old school boxing" that existed before modern boxing. This is simply modern boxing without gloves. And most of these guys wouldn't stand a chance against a pro boxer.
Boxing overall is not what it was, whether with or without gloves. Pro boxers aren't the standard they used to be and modern bareknuckle is just boxing without gloves despite people trying to make it out that because it's 'underground' it's more authentic, more tough, more real. It's not, it's just boxing that is unsanctioned by the official ruling bodies. It's not illegal as I said so not 'underground'. It's the betting part that's illegal. There's plenty of unlicensed boxing with gloves as well going on. We have boxing bouts in the cage as well alongside kick boxing and MMA. the standard varies from good to dire. Some of the licensed boxing is pretty dire as well though.
The travellers like the bareknuckle because it seems more macho and they don't like anything that is licensed anyway or at least anything they may have to pay taxes on, though there are two traveller pro boxers who fought recently amid a lot of smack talk.