"Laserdiscs in the CAV mode literally allowed you to access any frame or segment on the disc within seconds and you could run something like the Death Star explosion backwards and forwards like a movie projector at variable speeds"

And newer players do it with CLV mode, too.

Basically, MPEG is a forward-encoding process: Changes from one frame to the next are encoded, and anything that doesn't change is left as is. Now, in order to watch the film backwards, the DVD player must look at the frame prior to the one you are viewing. Needless to say, this is a tedious process, and it works for fast forward as well. There's a great deal of computation involved, which is why early players sucked at it.

LD, on the other hand, just shows whatever frame it's on, and FF/RR occurs at whatever speed you want with no delay. No muss, no fuss.