Some people would call removing you loved one's agency to make their own decisions abuse.
In the abstract, though, I think yes, if you see someone being abused repeatedly and you support and encourage them to continue going back to the abusive relationship, you are enabling the abuse.
I don't think any of us have any idea what the facts of the situation is. So it's not clear to me anyone is "enabling" anything.
(I also believe sex work is necessarily self-destructive, as it commodifies, commercializes and depersonalizes the closest, most intimate way of relating to and bonding with another human that we have.)
Your phrasing of "why do you let your wife..." implies OP can and should control whether his wife does this self-destructive behavior.
He can't, literally, and he should not try to.
He is responsible for his choices, not hers.
Yes, if he sees this as hurting her and he's not trying to persuade her to stop doing it, he's responsible for that inaction on his part, and I'd say he should take action.
But, he needs to always remember he does not and should not control her.
Obviously you should not use violence or force to cause a change but if my wife was working in a profession such as this I would absolutely give an ultimatum of either stop or the kids and I are leaving. Sometime tough love is still love. With that said I don't know OP's situation and they will do whatever they think is best in a situation.
That is knowing what you are going to do, and when, and communicating that to your partner.
It is not about controlling what they do, which is what the wording of "let your wife" implies (whether intentionally or not).
But you can't make them stop choosing to take the next hit.
All you can do is try to persuade them to stop.
Sometimes defining boundaries of what you'll tolerate is part of that, as I've described elsewhere in the thread.
That's about knowing what you will do and when, then communicating it to the others in the situation. It's not about controlling what they choose to do.