A lot don't bother to come back to do it anyway (they may have found the answer on another forum and just abandon thread on this forum and any others they've posted query on) .
Mostly those who want to tick their thread resolved will ask if they don't know how. You can always say in your posts how it is done so at least you will know that they know... but it is up to them if they do or not.
Not a big deal really, you get used to it. Fact of forum life - not just this forum.