It can partially solve the inrush current issue. There are still timing issues, if you slam a drive in you can shorten the timing of pin contact so much that its not effective. You also gain a real benefit in that one drive failing by something major, like a straight short, won't take out your entire system as the controller will detect the current spike and cut off the drive. Most hot-swap controllers also provide additional protection against things like pin reversal, ESD and accidental shorts on insert that you can't solve with just the connector. It all comes down to how robust you want the design really, how many failure modes you wish the system to survive.

EDIT: Those connector pins aren't normally solid gold. They are deposited metal (copper or tin) with electroplating of a few microns of gold on the surface.

Another reason to control insertion spikes is that when the first power pin hits you'll get a little arc (spark). This can cause small damage to the pins in the form of small chipping of the coating and/or carbon deposits(or oxidation of some metals). This contributes to a reduction in the number of insertions cycles the connectors will survive.