> They are averse to losing money (via needing to spend money to redesign systems, recertify interfaces, re-train pilots, rebuy new equipment and simulators, all of those reduce risk but are capital intensive).

Re-designing systems introduces risk and uncertainty. Being able to leverage existing pilot training reduces risk (because crashes have resulted from pilots forgetting they were flying X and applied training for Y). Buying new equipment introduces risk of manufacturing defects that wasn't present in the working one.