My personal theory is that it's a combination of both of those, with changing recipes and all that, + the way our tastebuds and brains experience the taste of things change throughout our lives for the non-sugary tastes, too, + changing preferences, + time and nostalgia affecting our memories of it.
I've thought about this a lot, lol
Oh my goodness, I love Bugsy! And look at that cute little paw curl!