People who post questions on this site are not entitled to answers which satisfy them. They are not entitled to any answers at all. Answers are provided free of charge by users who donate their time, effort and (hopefully) their expertise. They have no obligation to answer even if they have that expertise.
The more advanced or specialised the topic, the fewer users who will feel able to answer. Your questions are moderately advanced, so you should not expect to get many answers.
If you are not satisfied with the answers provided, the onus is on you to explain why. I can see only 1 comment by you among the 4 answers which you have accepted, and that comment (in How to induce artificial gravity?) was answered.
I can see only one comment to which you have not received a response, on the question Friedmann equations for an open and accelerating expansion.
Besides providing feedback on answers, you can also increase the exposure of your question (and the chances of getting more and better answers) by editing it to make it clearer or to provide additional context. This additional information should appear in the question rather than in comments, as recommended in the comments to your latest question Anisotropy and the Planck results. Editing the question bumps it to the top of the homepage, giving it more exposure. Comments do not do this, and are easily overlooked.
Older questions tend to be neglected. In many cases the asker has lost interest so answers are less likely to be accepted or to get upvotes. So users looking for questions to answer concentrate on those with recent activity. If you still want answers, you have to keep the question "live" by editing it.
And as others point out, accepting an answer indicates that you are satisfied with it and do not need other answers.
Users who provide suggestions about the form and content of your questions are trying to be helpful. They might not be able to answer your questions, but they can give useful feedback which will make your question more attractive to those who can provide answers.