What ongoing engineering goal is exemplified by the later addition of the Granny Gear?

The continuous push for more granularity in speed options for difficult ascents.

Even after the derailleur system won the dominant position over the fixed gear, the fundamental engineering objective remained conquering varied terrain with optimal mechanical advantage. The development of the Granny Gear, a sub-bottom gear ratio designed specifically for extremely steep climbs, illustrates this continued pursuit. This addition demonstrates that even successful multi-speed setups needed further enhancement to provide exceptionally low speed and high mechanical advantage for the hardest possible ascents, proving that the quest for engineering granularity in gearing was an ongoing process beyond the initial adoption of multi-speed capabilities.