Programming languages are (a bit) like Mathematics. You need to design new ones to solve problems your existing tools don't cope well with.
Whole branches of Math were created to solve problems. So were programming languages.
In the 90s I mainly used Lisp and Prolog for AI; doing that same research with my beloved Pascal would have been impraticable at best.
That said, it's true we have "too many" languages to address similar tasks. Consider it as an expression of pure freedom.