The reason everyone is opted in automatically is that SD is designed to give options to, and to be attractive to, potential buyers. They really don't want sellers picking and choosing which of the available postage methods they are willing to use - to be fair, that would rather drag us back to the pre-SD days.

I agree that it can be a bit of a pain. I've never used InPost; I don't know if they are punctual and/or reliable, and I don't know what I need to do to use a locker. However, I'm sure I'll cope if and when I need to.