The Italians love them. Nearly every vintage wheelset you can find or NOS rims are all tub specific.
Traditionally a tubular wheelset was way lighter than a clincher alternative but with modern tyres and latex tubes, or even tubeless, that gap has narrowed considerably. I wouldn't run tubs on anything other than a novelty bike. I have a set to go on my classic TT bike I'm building, priority is weight, speed and period correctness, I won't use it often or for any sort of distance but it has to be done!
Traditionally a tubular wheelset was way lighter than a clincher alternative but with modern tyres and latex tubes, or even tubeless, that gap has narrowed considerably. I wouldn't run tubs on anything other than a novelty bike. I have a set to go on my classic TT bike I'm building, priority is weight, speed and period correctness, I won't use it often or for any sort of distance but it has to be done!