Indeed, it's the chipsets that are the limit. The IP is complex, so there's no one who really wants to design whole new cut-down silicon to implement a "simple" USB 3 dock with fewer features to sell for less money. And since the chipset supports it, and technically you can't certify it as USB 3 without it (not that all these devices are fully certified), you might as well just use what the chipset gives you. In fact, in terms of implementation, that's probably the easiest as you just follow the reference design. So that's what they do.