This issue was discussed [very informally] at the NRA Range Conference in San Diego, CA in October.
Seems that for many indoor shooting ranges, about every 3-4 years, a customer comes in, rents a handgun, shoots it for a while, and then........well---you know.
Some ranges now do not rent handguns to loners who walk in to rent-and-shoot. Want to rent a gun?? Then bring a shooter-buddy. For whatever mysterious reason, folks will not shoot themselves with a companion along. Instead, they do it as loners. Various theories on this aspect.
To cope, the ranges insist on renting only to two or more shooters.
Go figger.