You need roughly 1m x 1m to stand still holding a gamepad, while being able to rotate 360°
You need an extra ~0.5m clearance on all sides to stretch your arms out if you're going to use 6D hand controllers, so that's 2m x 2m for a standing up experience with 6D hand controllers.
If you want to be able to walk 1m in each direction, then you need a 3m x 3m room (unless you want to keep your controllers stuck to your body).
But 1m is nothing so you really want at least 2m in each direction, which requires a 4m x 4m room.
And most users don't even have a 3m x 3m empty space to dedicate to VR, and probably ten times less then that have a 4m x 4m empty space.
You may think requiring 2m x 2m (from floor to ceiling) for just a 360° standing up experience is stretching it, but truth is my own space is roughly a 1.8m x 1.8 space and before I knew it I found myself both bending forward a bit on top of stretching my arm out as far as I could, which resulted in me banging my hand controller into furniture, so that's an extra 0.1 m missing on each side and 2m x 2m is in fact just barely enough for and adult.
Assuming most users will have to clear up just to achieve a full 2m x 2m empty space right next to their PC just to pull off that kind of standing up VR, then financially speaking that just doesn't leave much room for... room scale VR.
Meaning that outside of an impressive but misleading 4m x 4m demonstration booth, what makes more sense is developing motion sickness free hardware and software mechanics for creating unlimited movement within a 2m x 2m space.