The thing is, you're wrong.
Very, very little of what Obama wants or has done is even close to what the progressives of the left actually want. Health care reform? He enacted the model proposed by the Republicans and devised by a right wing think-tank to create a market-based approach to near-universal healthcare: if you think the left is happy with Obamacare, you're not paying attention.
Its simply *better*, and so we will stick with it. What the left wanted was a single-payer really universal healthcare, but we compromised and were willing to go along with the ACA as long as we'd get a single-payer *option*. Then that got dropped, but most of the left decided to support the ACA anyways because really, it was better then what we have now.
Obama is a centrist; center-right in most issues, occasionally center-left. There is nothing even remotely radical about anything he's done, there's been no great pull to the left. The left has gone a bit farther left then we were a decade or so ago, but that's been in response to the monumental shift the right has gone.
There's a wholesale assault on reproductive and fundamental voting rights going on from the right these days, which is just stunning in that these are things that *only* the most extreme of the right's base want.
On civil rights, surveillance, foreign policy, environment, business regulation, ... and on and on, Obama is not at all in line with what the left wants. He's just not as bad as what the crazy people on the far right want.
Yes, there are some narrow places where the far left and the libertarian wing of the far right actually agree, and its weird when it happens: but those are on very specific and very narrow issues. The problem with that libertarian wing is then they fall flat on their face in when the social conservative bloc of the far right has to be dealt with in primaries, and suddenly small government meets bedroom and private health, and oops.