I think I know why B&M's keep their humidity at 70%. Even seen someone walk into the humidor and start finger-fucking every cigar in sight? If the cigars were at 65%, they'd get a lot more split wrappers than they already do.

I speak of finger-fucking from lots of first-hand viewing at my B&M, where I hang out a lot. I'd say half the customers come in and have to pick up every damn cigar that catches their eye, and if they put too much pressure on the wrapper, the cigar will go POP and the wrapper will crack. It would be much worse if they kept their humidor at 65%, it's bad enough at 70%.