The reason Obama reaches out to Hispanics, gays, and Jews is that it's worth his time to do so. It's not worth his time to reach out to blacks. In a way it's sad. The black community has never had stronger political rights than it has today, but it's less relevant than it has been in 100 years, because it predictably votes as a bloc in every election. That can help a group in the short term, but it hurts if it becomes too predictable.
The Republicans don't care what they think or want because they can never attract their votes. The Democrats don't care what they think or want because they can never lose their votes. All they have to do is pretend that they care, and that's good enough. (Basically, public hostility to white people coupled with some lip service is enough. Actual results don't matter. If they did, people like Waters or Sheila Jackson-Lee couldn't get elected.)
By contrast, the Weiner open seat election proves that the Jewish vote is winnable by both parties. The Hispanic vote has proven over the last three election that it can also lean one way or the other and can be pivotal in many states. The gays lean Democratic, but many are fiscal conservatives. (In fact, most gays that I know are indifferent on the "marriage" issue and hard right on tax and spending issues.) Knowing that the Hispanic, Jewish, and gay votes are up for grabs, it's a much better use of Obama's time and political resources to reach out to them. Any kind of substantial work done to lure black votes is a waste of time for him.