Hi Gembo
For the simple reason that it saves everyone time to let people know how to find an answer to their question, even before they post it. A lot of people are on here a lot of the time and you see the same questions over and over again.
When you post a question - AB suggests some questions already asked that might contain the answer. It seems to a lot of us that these are being ignored, then the button is pressed and the question is posted.
You can also search in the bottom left of the screen for an answer to your question - this seems to be overlooked too.
Sometimes and this is getting more often, the same question appears further down the same page that the new question is asked.
There are lots of ways to look at it from lots of different angles, most of the time - there's no offence intended but sometimes it comes over a little harsh, similar to texting, when it's put into a short sentance.