The Space Shuttle used autogenous pressurization for its main engines / external tank, and the Delta IV is eventually planned to do so as well. And as you menti

The Space Shuttle used autogenous pressurization for its main engines / external tank, and the Delta IV is eventually planned to do so as well. And as you mentioned SpaceX plans to use the same system with their next generation of rockets. It is tricky to get working correctly and requires a larger up front engineering effort, but the payoff in simplicity of operations is significant. Additionally, it provides gaseous propellants that can be used for other purposes, such as attitude control thrusters.