Injector drivers and ignition drivers are part of the control unit.
The ECU is a computer, a packaged bundle of chips which plugs in to wires and does nothing but communicate to other components via those wires. That's what an electronic control unit means.
The driven devices, amplifiers etc. are under the control of the control unit. They are not part of the control unit. They're located in areas subject to much more heat and mechanical stress, and in most cases (ignition coils excepted) are mechanical in function.
Because...
The driven devices, amplifiers etc. are under the control of the control unit. They are not part of the control unit. They're located in areas subject to much more heat and mechanical stress, and in most cases (ignition coils excepted) are mechanical in function.
I'm not talking about the driven devices.
Here's a diesel example in video form:
https://www.youtube.com/watch?v=4k-G1dMgFUo
Here's one in gasoline form:
Sure they do. Take a look at the FICM failures with the Ford 6.0 diesel. In the gasoline world you'll come across failed injector or ignition drivers if you look hard enough. Failures due to environmental causes (like the wiring harness wicking hydraulic fluid into the control unit itself) are a thing as well.
It's not engine related, but BMW's late 90s-early 2000s five series uses a computer to control its lights. The failure mode is that your lights stay on as long as the battery is hooked up (fail safe). Unfortunately the IC that BMW used was discontinued by Infineon. I think a surface mount version is still available, but ultimately yeah these things wear out and you're largely at the mercy of the OEM.