Not just insurance
The other question is the recency and ability of an individual if the conditions are not CAVOK/wind calm.
Some of our PPL hirers are better than others and we can make a judgment on their ability based on how far back thee last flight was and our experience with them.
A FTO has to look at the possibility of an aircraft coming off the side of the runway and being U/S for a while is a loss of income due to the lack of currency of a hirer.
Of course that runs hand-in-hand with the legal requirements/dual checks etc.