Clerics as well, though in both cases it probably depends a bit on the specifics of the character and the setting. I can imagine a warlock's pact being power that 'can't be taken back', so that a jilted patron has to actively work against their Warlock rather than just 'cut off the juice'. Overall, with the very slight exception of Paladin, the idea of a 'fallen' class has seemed to been phased out
The struggle that creates, to me, is that *every* PC would be 'the exception' because of gamist concerns (I mean, do you ever see a fighter in Chain Mail for 'rp reasons'?). I would have liked some minor, but annoying, mechanical effects myself (takes an extra use of wildshape? Difficulty with concentration checks?). I could envision a subclass, or even background (heretic: background benefit: can ignore strictures of religions etc) that removes the restriction but still keeps it 'rare' in some way
Well... the more relevant point for me is: 'campaign settings were built with the assumptions and aesthetics of previous editions, so to keep consistency in those settings I maintain it' much more than 'old edition fluff applies universally to new editions'