Honestly, I think it's because the average American has about as much objective understanding of their own country's politics as they do about quantum physics--that is, virtually none (and most of the information is second-hand and/or heavily-biased by the media).
To be fair, there are a number of conservatives out there that I don't believe are making good choices for our country either. Let's not put on blinders and fail to consider the shortcomings of all parties involved.
But it drives me crazy when people listen to a politician (in this case, Obama, but there oodles of others) talk about all these nice, warm-feeling-inducing buzzwords, almost zero facts or real-world logic, and then back him 100% (because he's a *nice guy*).
Listen to some of the "speeches" these politicians give! Dozens of them go like this:
"Blah, blah, blah, bright tomorrow, blah blah, lowering taxes, blah-blah, change, blah blah, [insert lofty, unattainable goal here], blah-blah, more change, blah-blah, blah, blah, hope."
"Hope" is not a business plan or a strategy toward any particular goal, here or abroad. And words like "change", "better future / brighter tomorrow", and even "lowering taxes / balancing the national budget" mean absolutely NOTHING unless there is a clearly-outlined explanation of what these terms mean and exactly what plan of action will be used to bring about the desired result (as in the case of lowering taxes or balancing the national budget).
Consider the Obamacare Act. It made all sorts of lofty goals and yet has delivered on virtually none of them. In fact, the bill passed before many legislators even knew all of what was in it! YIKES! Something like 2% of the 49 million uninsured people that Obamacare was geared to target have actually signed up for it...and few of them have actually paid for it.
If we had taken off our "save-the-nation" glasses and put on our "let's-be-real-here" glasses before passing this hodge-podge, legal monstrosity, we might also have noticed that it's been costing several times more than originally anticipated (therefore the original claim that Obamacare won't skyrocket the national budget reeks of bullcrap).
Hopefully someday the rest of the world will catch on. It's not enough to say the right things and make people feel good. "Feelings" do not good politics make. Facts, reason, real-world experience, and a clear plan of action is what gets things done. Period.