I think there was a patent issue that forced SRAM to design a grip shifter much more complicated than it needed to be - the cable head is anchored in place and the shifter worked by an eccentric sleeve rotating under the cable. The more obvious design, to have the head of the cable anchored to the rotating part, was (I think) owned by Sachs, who SRAM bought in the mid 90s, when SRAM started making their own '1:1' derailleurs and shifters. THe cable change on these was likely a thousand times easier than the old eccentric slider design.