There is also the chance that they don't answer because they can't!
I "met" a distant relation through Ancestry and we became good friends. Whilst working on a mutual branch of our tree, she found what, at the time, looked the correct people emigrating to America and having children, so we added them to the tree.
Sadly, she died 5 years ago, but her tree remained on Ancestry for all to see. A couple of years ago, with new information on line, I discovered without any doubt that the information we'd added wasn't right, so changed my tree. Hers of course remains the same and I often get hints referring me to it and the wrong information.
I realise that you can check when a person was last on line, but that isn't always correct, as when I checked hers it did say within the last year, which wasn't right. So, there may be reasons why people don't respond!