Who do you trust the testimony of more?
The person who has an ideology in complete opposition to your own, but cites sources for any factual claims they make, and distinguishes between their commentary and the truth?
or
The person whose ideology is compatible with your own, but cites nothing that they claim, and interweaves commentary and truth?
Now switch the ideologies.
How about this one, who do you trust more:
The person who makes claims at odds with the general “consensus”, or generalized knowledge base, but cites sources for their argument, and backs up their claims with facts?
or
The person who makes claims in keeping with the general “consensus” or generalized knowledge base, but doesn’t cite anything?
Now switch the claimants.
Starting to understand why people ask you to cite sources?
If you are asked to cite a source, people aren’t saying you are wrong, they are telling you that what you just said does not fit in with their knowledge of the topic. Since no one here knows you personally (I assume) and can attest to your credibility or credentials (I’m not accusing you of posting false education credentials, but you easily could have, just as anyone else could), they have only two things to rely on to judge whether to accept your testimony: their knowledge, and your credibility. When what you say goes against their knowledge, they have to consider how credible you are. Many of us don’t consider you that credible, not in a small way due to the fact that you rarely cite your sources. When you cite your sources, you give people more information with which to consider your testimony and judge its credibility.