My sense is that "we need 99.9% uptime so solutions that require maintenance downtime are not acceptable" even though the lack of solutions is a bigger drag on uptime. But if your mandate is uptime, voluntary downtime is not at all an easy choice. You get blamed for voluntary downtime whilst accidental downtime is not directly going to be blamed on anyone.
There are quite clear paths forward and no shortage of prior art for the engineering portion, unless there is something we aren't privvy to it must be lack of incentives and bureaucracy.