That’s not to say you can skip end to end testing, but the more testing pushed to the complete system level will drive up cost and schedule.
If I were to put a fuel injector (system under test) into a vehicle, and drive it around a parking lot (E2E test), only to have the vehicle stall out. Is the fuel injector at fault? How would you prove that?
No, you pull out the component and you "bench test" it. Believe me, after many MANY hours spend fighting bugs where the extensive E2E suite passed, we finally had to go back to adding in unit tests for the small units under the surface. Not all... but many places.