A more stark example: why did we wait 2,000 years for the elevator? Archimedes had invented every component necessary in the 200s BC. It took til the 1800s for a dude named Otis to add one extra part that made it practical and safe, and soon they were everywhere.

Electric motors so every building didn't need its own steam engine, and cheap interchangeable parts manufacturing for the mechanisms that needed to be perfectly consistent in every installation to be reliable.