Forgive me for my ignorance. I am not familiar with boating at all. I've always been curious why boats are left tied up in the marina when a hurricane is approaching. Why don't they get evacuated/ towed to a safe place in another state?
As alluded to upthread, for many craft, there are logistics barriers and cost considerations that make it impossible to move them entirely out of the hurricane's path.
Here in Minnesota (where we have no hurricanes) most pleasure craft are trailerable. Generally any craft up to about 25' in length and 8.6' abeam can be trailered quite readily although even then a trailer, tow vehicle, and driver are needed and all must be capable of a longer trip. Oftentimes people who only use a trailer for winter storage do not keep the trailer in a truly road-worthy condition.
Boats up to around 32' long and around 10' abeam can be reasonably moved on a trailer but usually require a custom trailer, the services of a marine hoist or crane, and an oversize permit from the DOT. In many cases portions of the boat will be too high for bridge clearance on the highway and a certain amount of disassembly is required to make the boat roadworthy. Anything above that requires equipment, skills, permits, and planning beyond the abilities of the typical boat owner. There are custom haulers who specialize in this sort of work but there aren't nearly enough of them to move a significant fraction of the boats in Florida out of harm's way in a week.
Or why don't captains drive their boats to water that is not in the path of the hurricane?
Some do, but it takes time, fuel, crew, a boat suitable for the journey, and a safe destination, all of which pose problems. The questions of where to go and when to leave are also difficult ones.
Most of the safe harbors that might be considered are at least 500 miles away, far enough to be an overnight journey (or one of several days for sailboats) and beyond the fuel range of most boats not specifically intended for long-distance cruising. Most boats and captains aren't prepared for a voyage like that, and there is the troubling scenario of being stranded somewhere away from home but still in the path of the storm if the storm track changes or mechanical, navigational, or fuel logistics problems ensue.