So...why would I need to learn another language other than for the journey along a new path..?
You wouldn't. If you have the means to solve your problems already at your disposal then there is no
need to learn another language.
That said, learning new languages will broaden and deepen you perspective on the way you view and do things. Learning C will give you a deeper respect for how things work a bit closer to the metal, and learning the likes of Scheme and Haskell will broaden your view on programming in general. I could go on listing the various languages and how they will benefit your understanding of programming and programming languages but I think what you probably want to hear is this - the status quo isn't a bad thing in your case, but it will certainly to be to your advantage to learn new things.
HTH
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broquaint