I suspect this is one of those issues where the risk is small if it does not happen too often or too long. There are many such things in aviation, where a broken system is allowed to be broken for a certain number of days on the basis that the risk it represents is very small for that amount of time. If the system were to be broken for a long time, then there would be more risk, in particular if it is one of a redundant pair the other one might break down too and that would be a bigger problem.