Thigh holsters can create even more potential problems for users than some of the extended/drop duty holsters of years past.
Getting in & out of many common office chairs, and especially the driver's seat of a motor vehicle (although passengers can have their own issues in this regard), becomes a bit more problematic and annoying.
Having the leg-holstered weapon banging into everything that the outside of your thigh once pressed against, smoothly slid by or along, pushed against, or any number of other normal activities, can become a frequently annoying occurrence ... and maybe worse, depending on your activities of the moment. Navigating doorways & ordinary obstacles, as well as easily clearing some things (like fences) can become a bit less easy.
The lowered holster is not where it can be covered by an elbow, which can complicate retention practices, issues and training. Might also create more potential for things to "go wrong" if you're rolling around on the hard ground ... fighting in the mud, the blood & the beer.
A thigh holstered weapon is no longer at your hip, right? More hours and LOTS of repetitions are going to be needed for the user to be able to quickly & properly find, draw & present their weapon under actual stress. Ever see someone in training or range quals reach for a belt-holstered weapon that was no longer on their belt? Ties up time and conscious thought to resolve. That can become problematic in an actual encounter, to put it mildly. (It's also where shoulder holsters, ankle & pocket holsters and other non-belt carry methods can create potential training issues for users ... and that doesn't even begin to take into consideration any changes in the threat level design & mechanism used
I've got an early proto-type plastic thigh rig made by one of the big names in the business, back when they were first thinking about marketing something in the then-new market segment for LE/Gov users. I haven't used it even in training/range use for some years. I didn't have to wear that sort of tac gear in my plainclothes assignment, so it was only used for T&E, training, range use, etc.
It didn't take me long to realize I didn't want to use it, and my daily gear load-out didn't require I move my issued pistol off my waistband, anyway.
Personally, I'd leave it for the guys & gals that MUST use this carry method due to specialty assignments. Then it's another one of those equipment usage issues to be added & addressed.