Asset management. A team at the top, that "should" be gunning for the Cup year in and year out (i put quotations around should, because thats the general mindset around the league... But theres a reason why Chicago is so successful, and part of it involves bucking that trend) has had 45 draft picks over the past 5 drafts, while a rebuilding team like us have only had 34.
Chicago has a great prospect pool because they avoid losing valuable pieces for nothing via free agency. They traded away Versteeg, Brouwer, Byfgulien, Ladd, Bolland, Campbell, etc. for varying returns. Theyve recognized that they have certain core guys locked up that they can win with, as long as they give them a good supporting cast. They trade guys while they can, subtracting from that supporting cast, but it also ensures that younger/cheaper options are continually coming up the pipeline to replace those supporting cast players.
Kinda funny that a contending team is willing to move valuable players during their window of contention, but a non-contending team like the Leafs have been willing to lose guys like MacArthur, Grabo, etc for nothing. Had we traded them, we could be looking at our own Saad/Pirri/etc coming up the pipeline in a couple of years.