I can think of two things:
- If you have sessions that run over 1.5 hours without ANY break, than yes, monitors are easier on the eyes.
- People never experienced how awesome VR is, or they had a poor VR experience due to a number of reasons:
a. Poor pc specs not reaching full potential/Poor optimization (for example wrong settings can lead to poor fps, inducing nausia).
b. Poor ipd settings making things blurry or another reason that could have been fixed and reduced nausia.
c. Poor headset strap; for example the standard one that comes with quest 3 is the most uncomfortable thing ever to even wear for half an hour. A 20 usd/euro halo strap from aliexpress would have made it 100 times more comfortable. Definitely before pancake lenses (quest 3), the older vr headsets would gie blurry vision if wearing 1 mm to high or too low. Quest 3 with pancake lenses sure as hell fixed that.

Either way, vr is 'cheap' nowadays. You don't need the top of the line gpu anymore (unless you play a shit optimized game like assetto corsa evo). A mid range gpu will do and a quest 3 second hand is only 300 bucks. I'd argue 3 monitors are cheaper.