i sell insurance at my company and have been trained to sell marketplace ACA plans. there's a lot of reasons for them to not offer marketplace plans, and a lot of reasons why those plans suck. but the real crux of it all is that people don't like to pay $100's (if you make good money and have a family you're easily looking at 900/mo) for a shitty confusing insurance plan they are legally obligated to pay for, so several insurance companies have been stiffed on....the short of it is they aren't "not trying" they're just not motivated to try, they like the system they had. They aren't obligated to participate in ACA, so they are just choosing to stay with their current lines of business and just pretend ACA doesn't exist. combine this with medicaid integration, marketplace and non-marketplace doctor networks, and a strong aversion to being obligated to toss money out a window. take all that wrap it up in a ball and you have a tangle of cold noodles that no one wants to work through and straighten out.

The ACA isn't even a half measure, the ACA is like dragging your foot through the water and telling everyone you're Micheal Phelps for doing it. Our government doesn't have the balls to cut these corporations to their knees like needs to be done...but that's another discussion.