None of you have ever taken your seats out apparently.
The passenger seat has an EXPLOSIVE pre-tensioner mounted to the inboard side of it. The cover is actually covering up two cables that go down, then around a pulley and attach to the pre-tensioner. If the pre-tensioner were to go off the cables would be pulled forward and, thanks to the pulley, would pull the seat belt down, thus "pre-tensioning" it.
The driver's seat does not have this (at least not on the seat, I'm not sure what might be in the pillar along with the seatbelt reel). It does have a switch to tell if you're wearing your seatbelt or not.
As for the seat back pocket issue... My 2000 ZX3 had none on either one (side air-bag equipped seats). It now has one on the back of each seat thanks to the people at Katzkin.