The reality is that over the last, what, 40 years or so, the cruise ship industry has taken advantage of the climate, both physical and political, in that part of the Caribbean to do their business. In the past it has been mostly concentrated on Cozumel, but the island's infrastructure is saturated; for the industry to continue to grow it has to expand into other locations, and it is natural for them to pick locations where there are already onshore facilities.
Unfortunately for the people who live in these areas, what happened to Cozumel has demonstrated that the benefits to locals of cruise ship facilities being built near them are limited.