I think part of it is that at the top end of XC racing, those guys are phenomenal at riding with the seat up- if you’re currently one of the best in the world you don’t have that much incentive to upset things. And up-and-comers and amateurs are very influenced by the top guys.
Pros do sometimes use droppers- at Cairns last year a couple of the top 10 finishers had them (though Nino won, and didn’t have one)
Actually it’s pretty interesting I think because as time passes and droppers get more and more standard, less people will be good at descending with the seat up. I know I am, now- in the 90s I’d never even thought of dropping the post in the frame, everything was done seat up, now I basically hate riding without a dropper- so that skillset’s just gone, and I have no intention of getting it back. A lot of riders will just never really have it in the first place. So will that lead to more people doing XC racing with droppers, or will it be a barrier to starting XC racing, if you people feel they have to learn a different way of riding which they’d not use from choice? Or will it just even out and people’ll adapt to whatever the single best way is?