I've never heard of 6-6 as the official standard load (well, not until this thread), but at the CC where I used to teach, there was a tacit expectation that faculty would take on overload classes each semester (for pay, to be sure), making the de facto standard 6-6. In that case, research requirements were zero and service requirements minimal. I suspect it's the same at the college the OP is referring to.
+1
I willingly teach 6/6, but I make some serious extra cash. Research requirments are zero, and service expectations are reasonable. My life is balanced. IMO, what makes a big difference is experience. When I started teaching eight years ago, I taught 6/6 (as an adjunct) and worked 70+ hours per week. Now I work no more than 45 hrs most weeks, and I do a better job.
My class sizes are small (<25, usually <20), I never more than three preps, and I never have more than one NEW prep. That makes a difference too.
Why would the same workload translate to 70 hours as an adjunct and 45 as non-adjunct?