Why do ESs etc. very rarely have removable cavity covers for access to the electrics?

I've been thinking about this a lot. I'm not a luthier but I am a professional player with, I reckon, a pretty strong base of knowledge about gear. But I've never really known an answer to the above question.

I suppose it could make the construction process harder, but I also know it's not an impossibility because there are some scattered models that have had a rear cover - including one Gibson I know of that was a cheaper model, so I can't imagine it's a cost saving either.

And so, if you want to tweak electrics, change pickups or, heaven forfend, re-solder a dry joint, you have to poke around through a tiny F-hole. It seems like madness to me.

Anyone know why so few ES-style semis (or indeed semi-hollow or hollow guitars in general) have ever had this feature we take for granted on solid-body guitars?