I don't necessarily disagree that Quinn is "more suited to a reserve role" than Haseley - but we were discussing who might be the starting center fielder, weren't we? Or is your point that Haseley should be the starter, and Quinn the reserve (with which I think I agree, given current personnel).
Quinn is a baserunning threat - in both the minors and the majors, his SB% is high enough to be a net positive (a lot of "base-stealing threats" aren't, really, because they get caught too often). That has value... which in Quinn's case is offset somewhat by his vulnerability to leg muscle problems. But still, as long as he's able to play, he does bring that value.
So what seems to be the point here is that, as of now, Haseley is slotted as the starting CF (or Haseley/Kingery), Quinn is the reserve. Herrera will have to outperform Haseley to force his way onto the 26-man roster - and he'll have to do that over more than a couple weeks in spring training.
If Kingery is pushed to CF on a more regular basis (e.g., if the club signs another infielder and doesn't also move either Segura or Hernandez), then Haseley goes back to AAA, to play every day, and Quinn is the reserve CF (until he breaks down, my cynical side says).