These guys are losing money Mr. Top, lots of it. Those who aren't losing money are not getting much return on investment like Hard Rock. Anyways if Bally's closed, who would you lose access to? Caesars or Harrahs would just get licensed and pick up the Caesars sports and the 888 offering, maybe they will add another. If Oceans closed BFD, William Hill is everywhere already.
Point being there are still plenty of skins left and even some casinos without a license yet. Can't blame the potential closing of casinos for loss of access to books, its the book operators that are the problem.