Oh, sure, we learned a lot more about the characters as time went by. We discovered that the Joker had dived into a vat of chemicals, giving him his bizarre appearance and driving him nuts. And the Catwoman had amnesia, caused by a plane crash.
But in the Silver Age it no longer was possible to ignore an "origin" for costumed villains. Yet because of the very tight nature of the stories back then, the origin by definition had to be very brief.
And so the origins started to look very similar, particularly for Batman villains. The basic template was that the villain is mocked for something, and as a result, he goes a little cuckoo and starts using that something for crime.
Danny the Dummy:
The Wheel:
Mr Hydro:
