Through the Infinity Saga, Tony and Howard Stark’s adventures fuel a lot of the main developments that form the culminating picture we see in Avengers: Endgame.
Most importantly, Robert Downey Jr’s performance as a Tony facing mortality and responsibility for the first time sets up his character’s overall function in the MCU.
We not only start to see a world where heroes are starting to come into the public eye, we also see the legacy of the Stark family building the bridge to the future.