Comment by ronsor

There are some reasons. As a satellite operator, the worst thing that can happen is getting locked out of the satellite for any reason. So the risk of implementing a “new” technology that has a high risk of locking you out if you lose the keys for some reason sometimes outweighs the benefit of increased security. So I think there’s some work to do in building generally applicable key management practices and backup ways of reestablishing a command link.

Embedded guys don't like command authentications, I think because it's an SPoF with probability attached that are repeatedly tried. They know bits flip and program counter skips, and so they even avoid use of "or equals to" conditions for loops. But they're using signature enforcement in cars nowadays, so that particular fear should be slowly subsidizing.