The Colorado State Patrol carried cross-draw for years. They didn't have cages in the cars and transported prisoners in the front seat. Cross-draw gave them more security that way. Now they have cages and don't do the cross-draw thing anymore.
A lot of guys who do long stake outs, or long distance prisoner transfers in cars prefer it. The don't have to sit on the gun, and can get to it even with the seat belt in place. With a regular strong side holster you may end up grabbing the seat belt buckle instead of the gun, or get tangled up in the strap.
Cross draw is an option for FAMs and others who fly a lot, like the PD helicopter crews. Again due to seat belts, arm rests, and the nature of some "bucket" style seats and so on.
Retention is an issue. But training can overcome that. They also don't conceal as well. Sweeping your weak arm, or your other people is an issue.
My biggest issue is muscle memory. I always mount my stuff in the same places so I always reach for the same spot. My duty holster is strong side high ride to match my off duty holster, and so on. I'd hate to instinctively reach for my gun where it normally is and find it not there. The ensuing delay could cost me my life.
I don't wear one, but if I was flying a desk or an airplane, I'd consider it. Maybe. But I'd have to train with it a lot before I adopted it.