I was just wondering this, as I'm under the impression that it's something people have gravitated towards or arrived at under a wide variety of circumstances.
For me, it was the realisation that the current global trade system, aside from being massively destructive on all levels, is not something we can rely on for long. So we need to take care of ourselves and our communities in the least resource-heavy ways we can, and to plan for the long term too. As in, centuries ahead.
As well as that, I'm partial to anything that means you can gain more for less effort.