Most large companies (and even mid-sized ones) have some kind of "technological environment of choice" that sort of given (three languages is already not so bad). It does not means it cannot change or be lifted for a specific project, just that it is "what you are supposed to use", and that you are expected to provide heavy arguments to be allowed deviate from it.

In most situations, this is actually wise : behind development, you have a whole process (deploy, quality control, etc), and they will have the required tools and expertise for the languages they use on a regular basis. And when you start a project at a large company, you know that other people will take it after, so it is easier if it is close to the company technical standards.

Having written an application in Ruby in a Java shop, I remember protesting on the "rewrite in Java" that happened just after the prototype phase. With some distance, I think I understand the decision.