Implying focus sash is the only thing Dugtrio can use...
CB Dug can be a very easy/cheap way of taking out something that otherwise annoys the rest of your team, it has priority too so depending on the situation, it can beat other priority mons too (ofc there's a bigger risk in there).
Orb Dug is pretty annoying too, yes it has less longetivity and it can't beat shit like Blissey anymore but it loses the downside of being locked to something that can be setup on. Saying it loses to Scarf/Priority/Jesus Christ is pretty meaningless since Dug will probably achieve what it's supposed to anyways (Uncompetitive RKs/Trapping). And even if none of that works, it can still make use of Memento.