The differences between standard libraries, programming idioms, communities and ethos often play a large role in defining a new language, so surely sharing a standard library would in many ways defeat the point of trying something new?
A programming language is not just a spec and a syntax, it's also a way of seeing the world - "The limits of my language mean the limits of my world.", so to get a new way of looking at things, you also need to reinvent the basics to some extent, and rethink how (for example) basics like errors, threads or strings are handled.
Personally, I think it's useful to have a multipolar programming landscape, even if it sometimes leads to duplicated work, because it can give you a fresh perspective on old problems.
A programming language is not just a spec and a syntax, it's also a way of seeing the world - "The limits of my language mean the limits of my world.", so to get a new way of looking at things, you also need to reinvent the basics to some extent, and rethink how (for example) basics like errors, threads or strings are handled.
Personally, I think it's useful to have a multipolar programming landscape, even if it sometimes leads to duplicated work, because it can give you a fresh perspective on old problems.