The paradox of choice and duplication of effort are very real problems. Let's take web app development for example. We have PHP, Python, Ruby, Java, C#, etc. Each language has their own set of libraries/frameworks and it takes a lot of time and effort for a programmer to learn all of them. I've been developing web apps for 10 years and yet, I couldn't contribute to a web app written in Java. What if instead of having X libraries in Y languages, we had X*Y libraries for a single language or X libraries of Y higher quality for a single language?
Standardisation has lots of benefits.
The web standardised on HTTP/HTML/CSS/Javascript and it enabled the creation of a massive ecosystem of tools, libraries and pool of developers. Front-end developers can easily switch jobs and contribute to other projects. I personally dislike languages that compile to HTML/CSS/Javascript because I think standardisation trumps their benefits. C is a de facto standard in the embedded world.
In my opinion, sometimes the hammers are so similar (e.g. Python/Ruby) that we should just collectively agree to only use one.