Because core top 6 players change teams all the time right?
Also Habs are in advantageous cap situation with their top players. None of the young forwards will earn 8 M for the foreseeable future. We will live and die with Suzuki, Slaf, Caufield, Dach, Demidov and one more to add through UFA once the team reaches the next step.
NHL team building is not like EA Sport. It's hard to move big contracts. Ask Toronto how easy it is to trade core players.
Habs being in an advantageous cap situation helps in any future trades.
Not sure why you bring up Toronto, as their top players cap situation is the exact opposite of ours, of course it would be difficult for them. Not to mention, there's no indication they even wanted to move any of their core; they kept wanting to 'run it back'.
Saying 'the habs will live and die with blablabla' doesn't prove a point. I'm not saying I disagree but yeah it's easy to see why they would be happy with good young players at a reasonable cap cost.
Technically though, anything is possible and IF we had drafted Michkov or Leonard or Joe Blow from Saskatoon, there always is an option to move a similar roster player if the team felt inclined to do so for whatever reason.