the utility company is usually required by law to b[u]y power from your rooftop solar at retail rates IF the customer has opted to hook into the grid. If they are not hooked into the grid then there is no requirement (nor could there be - they are not hooked in).

In Indiana, the utilities generally buy at a steeply discounted rate and then charge at a steeply inflated green rate for a nice profit, so it is not really beneficial to sell power to the utilities, but clients also have the option of netting their power against their consumption at a 1:1 ratio, so most do that (if they tie in). If Indiana were to try and pull a similar stunt, there should be a hue and cry that end user producers get a retail rate instead of the pittance utilities offer now.

EDIT ADD: I would also add that with the 1:1 net (as opposed to the sale of power), they do not have the option of making money, but it usually is still more beneficial to go the net route.