It may not increase their overall profit, however it significantly decreases their overall loss.
Fully 70% of all motorcycle accidents are the Cager's fault, typically involving violations of right-of-way. Juries tend to award big buck settlements to the bikers who survive and take the transgressors to court. This has practically become a cottage industry for legal firms. In Milwaukee alone, three legal firms claim this as their specialty; their advertising budget is impressive . . .
Here is just one example; look at the payout from these guys . . .
The easiest way for the insurance companies to mitigate these losses is to find a way to reduce the number of motorcyclists on the road. Fewer bikers = fewer payouts.
Every state that has enacted mandatory helmet laws has seen significant decreases in motorcycle registrations immediately following. Conversely, every state that has recinded mandatory helmet laws has seen significant increases in motorcycle registrations. Your fine state of Florida is a perfect example; ridership is increasing now that the helmet law is gone. Pennsylvania is next; watch as the number of motorcycle registrations increase there as well. Bottom line, insurance companies' profitability goes up when ridership goes down.
Ride safe, bro!