http://en.wikipedia.org/wiki/Confirmation_bias
You are dismissing information that does not agree with your argument and using false assumptions as a basis for it. The anecdotal evidence you provided is near useless due to it being a miniscule sample size. You are assuming the majority of players do visit and post on the forums, that is false. You are assuming that the majority agrees with you on wanting the ability to mail heirlooms cross servers, you do not have the information necessary to make such a statement with certitude or have not provided such information if you do possess it.
As I have stated multiple times I believe they have other projects to work on that are much higher priority due to them having higher relevance to a larger number of people and do not wish to detract from those projects for such a minor feature. I am stating my opinion and saying it is such, I am not trying to masquerade an opinion as fact.