Well to be honest I see no evidence in anything you've done or they've done that would imply that your reasoning has any weight. What I mean is you're asking questions like you did something wrong. What is wrong is that you're assuming that you are causing people to not want to talk to you and without any more detail on what your relationship is like with any of these people it's kind of hard to make any kind of analysis as to why they haven't responded.

there are a number of reasons that can be going on that would have nothing to do with what you've said, you needing them too much or anything like that. I would have to ask, how long has it been? Based on typical emailing is it a lot longer? If they are types of people that don't use email constantly, that's just that, they dont' email as often and that also is not a reflection on anything you are doing wrong.

What was the email about? How long has it been?

Finally, have you asked why they haven't responded?