They're gold players to have, but theyre always moved/available. Tanev (UFA), McCabe (Trade), Carlo (Trade) and thats just how the Leafs acquired theirs.
Gudas (UFA), Trouba (practically a salary dump), Manson (trade), Severson (UFA), Mikkola (UFA), Edmundson (UFA), Savard (trade/UFA), Faulk (trade), McDonagh (trade), Cernak (trade), McNabb (expansion, but was a trade acquisition by LA previously), Roy (UFA)... those are all somewhat similar middle pairing d-men and how they were acquired. And that list is not exhaustive.
Meanwhile the list of Danault types thatre moved would be much shorter. And when inferior players like Laughton are going for a 1st+...