I'm not be the best guy to answer as my rep indicates but I will answer anyway :)
Why is this happening?
Because your site is on the main page of Ubuntu.com. What does it say? And if you get stuck Askubuntu! It doesn't say read the docs :)
Ubuntu is the most popular Linux distro out there, every time a user finds a silly problem, he comes here (I am no different).
More newbies than experts, this would be the result and more! Experts would get tired of answering questions, they want real good questions, otherwise they won't answer.
(When was the last time you saw Jon skeet or jeff answering questions that have less than 10 votes? Jeff left SE because it's not challenging anymore, this what I believe. Skeet doesn't count, he's a robot :P)
And let me ask you, didn't you ever think about just dumping Ubuntu and trying a more challenging experience like Arch or FreeBSD? Or maybe just different experience like Fedora? If you really love Linux then yes you did :)
What does it mean? You're no longer active on this site, either because you got bored answering low quality questions or because you decided to try another distro.
What we can do to improve that?
Declare martial law like they do on Arch forums, don't answer newbies unless they read 200 wiki pages :) Maybe even close them. That's how SO does it. SO isn't doing much better than this site, it's just that they close so many questions
(and I hate them for that, but if you think about it, it's the only way to deal with so much questions, or maybe hire 2 more Jon skeets or Castro :D)
I do not have any other solution, this solution is effective, newbie questions should not end up here in the first place, ubuntuforums.com is the right place for those questions (I am a newbie too).
And there's another issue, that I wanted to discuss on meta.SE but they'll vote it down anyway, you see SE is becoming huge, really huge. Too many sites, for example, you'd prefer to answer Ubuntu questions on superuser or serverfault or unix.SE or here, you can't maintain a community that huge, some sites will be less active than others, it's inevitable.
If Ubuntu becomes a rolling release, (it's being discussed) then there will be far less questions, because there will be 1 version, and you wouldn't see an issue on 12.04 or 13.x, one version for everyone, similar issues for everyone, and I hope it would be more stable like Manjaro not Arch.
Another thing are the questions related to driver support, on superuser you don't see that many questions related to drivers because Microsoft somehow supports so many hardware out of the box, if ubuntu can do that, then the number of asked questions would be so much less than today.