It's called "rebuilding." Hextall filled out the back of the roster with low cost scrubs and saved his assets for the draft.
Hextall has collected a bunch of talented young forwards but it takes a while from the draft to the NHL: Frost, Ratcliffe, Rubtsov, Laberge, Kase, Allison, Laczynski, Farabee, O'Brien - but we're talking 1-3 more years.
Which is why Fletcher was looking for a young forward who was NHL ready, not another prospect who won't arrive for a few years - the cupboard was fill, so unless you're getting a top 20 pick, why bother? And I doubt anyone offered a 1st for Simmonds. A late 2nd is likely to be another NAK or Bailey. Whereas Hartman can help right now and for the next 2-3 years on a low cost RFA contract.