Thing is you limit the market then. Yes, a lot of teams would likely want to get Kreider at the deadline and give up assets, but you might have 3-4 teams with interest.
Right now, the whole league (roughly) could make the move. They'd also get him for 82 games instead of 30ish games. Larger return, plus they can talk an extension this summer.
Those teams that believe they are on the bubble would probably pony up on the asking price now knowing they will have him in their top 6 all season long.
Not to mention, if there is a 1st round pick involved in the deal, there is the off chance that management misreads their team and you get that lottery pick. It wouldn't be like the Duchene trade, but imagine moving Kreider to a team like Edmonton, getting their 1st, and that team missing (which is realistic).
Having two lotto picks (let's be honest, this is still not a playoff team) would elevate our "build" to levels we probably fantasized about.