It couldn't be because of the decay of an amoral society......
Noooooo....... that would be JUDGMENTAL. Only right wing religious fanatics are judgmental.
While religion has historically provided an important "parenting for adults" constraint on society, I'm not convinced its really about "decay of an amoral society", so much as the proliferation of immaturity itself...
People simply have no expectation that they are responsible for anything - their actions, their economic safety, their physical safety. Urban civilization feeds on inherent laziness (not of just humans, but all organisms) and amplifies the infantilization people normally experience when societal structure starts providing answers/solutions that you would otherwise have to seek for yourself.
If retirement is a big question that we all must answer individually, then, on balance, we all retire as more educated consumers of the retirement options...
If there is a "default", even if that default is sub-optimal, fraudulent or short sighted, then a large chunk of people will fall back to it... You don't have to grow up until someone kicks you out of your parent's house. It may be that where you end up is better than your parents house, but I think its safe to say that a run-away majority of people would have stayed with their parents far longer if they weren't encouraged/forced to leave...
Now, I suppose you could argue that "morality" offers an answer in various ways such as defining sloth as a sin, but the practical reality is that "reality" provides the more reliable motivator (again, that reality being, that your parents will no longer support you or protect you).