Expressiveness isn't always a positive language trait in a corporate environment. Java is extremely popular partly because its easy to learn, easy to write, and easy to read. Mediocre programmers can still be very productive in Java, even if their code is wordy and inelegant.
Furthermore, it's easy to abuse expressive languages. An expert java programmer can refactor poorly written code quickly. The more expressive the language, the more difficult understanding and refactoring horrible code becomes. LISP macros are a good example. Macros are powerful tools in the right hands. In the wrong hands, they can result in confusing and hard to debug code.
LISP is a risky choice for senior management. If things go wrong, no one is going to blame management for picking a popular object oriented language backed by a major corporation like Oracle or Microsoft. Its much easier to hire programmers with experience in popular, easy to learn languages.
Even progressive companies willing to use a more powerful language usually don't choose LISP. This is because many of the newer languages try and compromise by borrowing powerful features from LISP, while staying easy to learn for the masses. Scala and Ruby follow this model. Bad programmers can pick them up quickly and keep writing the same mediocre code that they did in Java. Good programmers can take advantage of the more advanced features to write beautiful code.
Parentheses are not the problem. Haskell is an incredibly powerful and expressive language with a syntax similar to Python or Ruby and it hasn't been widely adopted for many of the same reasons as LISP.
Despite all this, I am hoping...
Clojure has a chance of becoming popular. It runs on the JVM, has great interop with Java, and makes concurrent programming much simpler. These are all
important things to many companies.
*This is my perspective as a professional JVM programmer with experience in Java, Clojure, JRuby, and Scala.