What the problem with being polite ?
You will will find that people on SO are usually very polite in day-to-day communication. However, questions are treated as something that is detached from the asker. It's about the content, not the person asking it.
While this may appear rude at first, it really is an incredible social quality, because it implies that a good question deserves to be answered no matter who asks it.
It also ensures they can, if needed, be edited and have the lasting value for future generations they are supposed to have.
I see what you mean, but it's just a question of culture, and easy to get used to. I personally wouldn't edit somebody else's question just to remove the salutation, but it is within the rules and bound to happen occasionally.