There are a lot of snobs in the Lisp community. They can't stand the thought of Lisp going mainstream, because their language is too beautiful and perfect. Every language has them, but Lisp seems to have the highest ratio of snob/regular person. I love the language, but the community is not as good as others.
edit:
I'm getting downvoted by the snobs themselves. Hilarious.
This may be true of the Common Lisp community but the Clojure community seems to be very welcoming and I think one of the more exciting communities around today.
As the famous "Brief, Incomplete, and Mostly Wrong History of Programming Languages" [1] essay puts it, Lisp's key techniques are "recursion and condescension".
As e certified smug lisper(you get to be one when another smug lisper calls you one :), I would say that there are many of us who just don't care whether or not lisp gets more popular, but I don't think I've ever come across anyone who would intentionally drive away new users(except for obvious trolls, who come to #lisp and ask what it is used for, and get angry when we answer: "Writing software", one even called us cts :).
I don't really mind more popularity, but my definition of a mainstream language is "The non-technical boss prefers it, because of reasons completely unrelated to its technical qualities.", in which case I agree with the snobs, we don't need that at all.
But if by mainstream you mean "It moves up from its current position as 33th most popular language on github", sure, why not. If by mainstream you mean "more companies start using it for useful software that makes money": http://this-plt-life.tumblr.com/post/36425247242/when-i-hear...
I consider Common Lisp to be a tremendous success, some of the coolest software was written or prototyped in it, including many language implementations. Not to mention what a tremendous achievement it is for a modern lisp system to be able to run 4 decades old code with little or no modification. Being mainstream was probably never a design goal, but the things listed above are, and that is probably why many lispers simply don't care about being mainstream, the language is not optimized for that at all. I don't thing that makes lispers snobs, they've just self-selected for people who can work with less community support. It's like a low-econ game of starcraft :)
edit:
I'm getting downvoted by the snobs themselves. Hilarious.