Justification of user-created languages to gain an advantage in the future
In it @zocky asked about the justification of using ultra-short languages specifically designed for code golf to win challenges.
On my question wasn't really the right place to post the question, but seeing as how he has a point, I am re-asking it on meta.
My question is this:
Why should we allow people to make their own languages to solve problems?
I know we have rules like languages have to be pre-existing, have an interpreter, etc. but what justifies the use of languages built to be ultra-short? Like why should we not be constrained to languages that are used elsewhere?