A) I doubt you need a $20 component to register a key press and do some canbus IO B) If you did have a $20 microcontroller for Canbus control of a window motor

A) I doubt you need a $20 component to register a key press and do some canbus IO B) If you did have a $20 microcontroller for Canbus control of a window motor driver but it saved $19 in extra wiring/labor (driver controls usually route to all windows), provides reliable debounce, automated one-push-to-open, and allows things like holding keyless lock to close all windows, it's totally worth it.