Tubs on the road have a number of advantages that tubeless can’t replicate eg more ’round’ tyre profile, much higher pressure capability, far better performance when punctured (a well glued tub should stay put far better than any flatted clincher). Not to mention lighter rims.
Conversely the biggest benefits of tubeless on MTBs – lower pressure – is rather lost on the road, and the sealant is less effective at sealing punctures on very high pressure tyres.
So basically… tubeless on the MTB, tubs for the road, they’ve been right all along!