I'm not sure how easily you could accommodate different gearing variations on a derailleur system, because the gears have to have points at certain intervals where they "catch" the chain and pull it onto the next wheel: it isn't done exclusively by the derailleur itself. There's also the matter of needing a longer derailleur cage for a wider gear range. I'm sure if Shimano et c had worked out a way to make money from offering fifty combinations they'd be doing it by now.
Yes if there was a need for a larger cage that would be included in that option. I'm not sure I understand the point about catching the chain. How does that preclude offering say 11-25, 11-30 and 11-36 options?
I wasn't really suggesting offering fifty combinations but 2 or 3 would be nice. I struggle with climbing hence why I have ebikes as well. I love road bikes but the fact that typically the best they offer seems to be 34/34 bottom gear. I find it ridiculous that the lowest you can realistically get on an entry level bike is 1:1, even on Claris and Sora! Shouldn't they be making the sport more accessible? So you buy a bike, you come to replace the cassette and realise you can't actually fit an 11-36 because of the cage. Or you think of fitting a sub-compact chainset but it seems it's not as simple as that either!
I do wonder how many people quietly give up because they can't get up their local hills. Or rather how many more would stick with it if they could get up with more realistic gearing aimed at real people not racing snakes.
Maybe they worked out they can sell more bikes if they divert people into buying a gravel bike as well.