Yep, supercab popularity has decreased significantly when crewcabs went mainstream.
Comfort is one thing, access is another.
If you park in a parking lot, next to other vehicles, and have someone in the back seat, it is an exercise to get in and out. Hard to understand until you try it.
I'll give it a shot:
Driver gets out, then opens the back door, rear passenger gets out. Now you have two people (or three!), that are trapped in between two open doors. Both people must now move into the area of the open front door, crowding together. Then the back door is closed, now both people must move out of the swing area of the front door, so the front door can be closed. Then you hear the benny hill song playing... Oh, and you do the whole thing again when it's time to load up.