The Jazz don't seem to have missed Josh Howard that much. The point you're making seems to be that having an additional young player is a net negative.
Besides that, it's not as though the Jazz are trading their franchise player here. There are and can be no illusions of that. What anyone is getting from Howard after this year is anyone's guess. Because of his history (mix and match off-the-court stuff, injury problems, and age), his future AND his value is even more nebulous. He is not in the Jazz's medium to longterm plans, this has been known and told from the start. Josh Howard is using the Jazz to resurrect his career, and if the Jazz are smart, they'll seize on his resurrection to add something that they can work with in this renovation (success to this point doesn't change that this team is under construction). Because of this history, where he sits in his career, and where he sits contractually, there is a short-list of destinations that would really want him now (real contenders) and have something interesting to give in exchange. OKC is fine, they've let their cake bake and it's looking nice. Portland has too many perimeter players demanding time as it is. I think SA is pretty well set in their rotation as well and I'm not sure what they'd be willing to give that I or the Jazz would want. The Lakers aren't contenders (yet), but I wouldn't really want to help them, and I'm also not sure how psyched I'd be on any of their young players either. Same with Dallas (who probably don't even want Howard). Same with Miami. Same with NYK (even though they're not contenders). Boston are on their way out the door. Indiana are fringe contenders and don't need him... But Chicago? They're knocking on the door and could really use a player like Josh Howard since they don't have a lot of breadth in terms of scoring bunch and all the wings besides Deng are unidimensional and/or not that good (yet). And they happen to have a player that I (and a lot of people) think is an intriguing prospect.
The bottom line is that the Jazz don't have anything resembling a real SF in five years, why not take an incredibly low-risk roll on this kid if it's possible?