I noticed that meta seems (in terms of the rate of questions) very slow compared to the main site. Does that mean that we can get rid of meta and use it only for high-ranking users and for people to look at for site policies? (Or at special times like elections)
I suppose this is ironic for me to say -- I participate considerably more than average on meta, after all -- but it is a very good thing that meta is way less active than the main site.
If there were as many questions, answers, and edits on meta as on main, it would mean that about half the effort that went into Ask Ubuntu would be going into writing and reading stuff about writing and reading stuff about Ubuntu, and only (the other) half into actually writing and reading stuff about Ubuntu.
The front page of the data explorer currently says Ask Ubuntu has 253 thousand questions and 331 thousand answers, while Ask Ubuntu Meta has 4.5 thousand questions and 6.8 thousand answers. So meta is slower indeed. But surely we do not need one post about the site for every post about Ubuntu!
That would be very inefficient.
(It might also lead to unflattering "How many Ubuntu users does it take to change a lightbulb?" jokes, with punchlines involving how many would be involved in changing a meta lightbulb first.)
As for why meta cannot simply be absorbed into main, I think this would not work very well, because without an attempt to draw a crisp dividing line, we would get questions that are partway about Ubuntu and partway about the site, and neither aspect of the question would really get answered properly.
No, Meta will not go away, as it serves a lot of useful purposes.
We tend to push content disputes over items to meta discussions, and we also have requests made for different changes to the site (feature requests, bug reports, questions/discussions of what is on scope, etc.), disputes over "why was this deleted" for questions, answers, etc.
Meta serves a very important critical purpose to every Stack Exchange site, this site included. It should not be removed.
Meta is slower than the main site because Meta is a site about the Ask Ubuntu site. That's why it's 'slower'.