@EEngr and MYvol
The seat belts on aircraft are the simplest money can buy that will meet the type certification tests. Car manufacturers would not dream of using such basic restraint systems indeed they would be illegal, yet their collisions are far less severe. It would appear that the specification for aircraft seat belts is more to stop people being thrown out of the seat in turbulence than for safety in a crash.
I would imagine that pretensioned seat belts as found in cars would have pulled the pax into an upright position with heads back against the seats and there may well have been less spinal and facial injuries.
If seat belts were designed for safety they would be inertia reel seat belts with pretensioners and as a minimum lap and diagonal or with a full harness design. However, as I pointed out above, in the beancounters' calculatons the weight penalty and subsequent fuel cost exceed the safety benefit.
Only a change in type approval to mandate better seats and seat restraints will change the current system.