Most are digital on Steam, Viveport, Oculus store (some good exclusives there), there's even 1 on EGS. If you mean Quest, it has a built in Oculus store with its own versions/titles (in stand alone mode, if connected to PC it's like the others), some as cross-buy with the PC version too.
The only physical VR stuff are some limited releases for PSVR iirc. Maybe I've missed some PC game that got one. Generally all modern devices can play any game. Oculus, Index, WMR, Vive, they all work via Steam and Viveport.
But the Oculus PC store is locked down to Oculus hardware officially, though there's a fan app to make other devices compatible with it, rebind their controllers to match, etc., so people can play the good exclusives there, otherwise it's best to use hardware-agnostic stores like Steam.
Some older games may only support specific kits, newer games generally support everything and you can always rebind yours to work with the rest but it may not be ideal given controller input/angle differences if the developer didn't bother, but they're generally lesser games anyway.