Honest answer....
Politics....more specifically "fishing politics"
Tools for catching lobsters (diving, not traps) in the "old days' were hand grabs, stick&nets, & bleach bottles {ugly but true}. For lobsters it has been trappers (90% of capture) and divers (10% of capture). Finger pointing has gone back and forth on which "tools" are allowed including many different traps or 'un-attended/soaking' devices that also catch fish. It's a very complex issue but current rules have been stable in FLA for about 3-4 decades. In Maine, Non-residents can't dive for lobsters, but in FLA everyone can dive for them. Politics.
The 2nd part of your question is location- Florida vs Northern states. The answer to that is simply the gulf stream and different species. Technically we don't have lobsters in florida, we have 'Crawfish". Maine has lobsters. The gulf stream bring all the baby lobsters into florida and they are called Recruits. 98% of our lobsters are born outside of florida and arrive via the central america gulf stream. You could theoretically remove all the Florida lobsters from the water and it would begin repopulating immediately with recruits from central america riding the gulf stream up. It's almost impossible to 100% make them extinct. This is not the same as Maine lobsters that are only located in those northern states.
Now someone is going to say 'what about california ??'. I don't have an answer.