The number one deciding factor for customers is location. Coming in a close second is security. In a far distant third is price.
Self storage employees can only access your unit in the event of an emergency, eviction, or a warrant from law enforcement.
For self storage facility owners, one of the top up-sells is insurance. Almost everyone buys it, again, for security (and peace of mind).
Unfortunately, this idea decreases security rather than solving one of the biggest customer pain points of renting a storage unit.