Just the opposite, actually. I could see why you would think this, but SE originally didn't offer rank rewards for party queue. It was meant to be a "for fun" mode, rather than a serious mode. The community went up in arms demanding rewards for it, so they changed their minds ... then people realized that they could win trade using pre-mades, and that mode went to hell in a hand basket.
I hear that it's doing well, right now, but win trading was a serious problem last season. It got so bad that people actually requested that SE remove rewards from it, even after fighting so hard to get them implemented. I haven't heard much about win trading on Primal this season (though I hear Aether is still having a tough go with it), but you still need to have a regular schedule to participate. It's kind of a give-take situation at the moment. You either join solo-queue with open queue times and a good chance to have a completely crap party ... or you join party queue which had strict queue times and the small possibility of win-traders ...