and I wonder why those sites accepting them do so. Is it that they don't have any idea of the scam allegations on 1xbit or they are incapacitated taking them down once it's on their sites?
Money is the reason why they are accepting them; since they are already known to be scammers by most people, they will have to offer a higher pay amount than usual.
Yes, they won't bother, they won't also care about their customers wellbeing, and they won't also be held responsible for any losses. This is because there is always an ad's warning and a TOS that state that "This site or platform is not in any way associated with any advertisement shown or displayed within their surroundings" or something of that nature. I can't recall where I saw this. So if anyone comes after them for any form of scam report or accusation, they will likely use that to defend themselves.