His family won't settle in SPL it's a new country it's got different culture from America. Messi's family are happy in Miami he's got children so he doesn't want to change their school. Al Ahli's offered a mega contract so he'll make a decision which is best for him & his family.
If Messi's going to join SPL he's going to get a mega contract. Cristiano's new contract with Al Nassr's given him power & wealth so if Al Ahli want Messi they'll have to offer Messi a mega contract. His family likes Miami it's home for his wife & kids so Messi's going to change their lives if he's going to SPL.
Yeah that's just it, to leave Inter Miami they will have to offer him something huge, something that he can not reject, something very tempting that even his family can't reject so he can try to reconsider but other than that I don't see any reason why he would want to join them.