Same reason Perl got a bunch of biotech libraries and tools at the turn of the century: a good enough language in the right place at the right time. Ruby's big

Same reason Perl got a bunch of biotech libraries and tools at the turn of the century: a good enough language in the right place at the right time. Ruby's big disadvantage is that until Rails happened, it was relatively unknown in the English-speaking tech community. And though it has begun to broaden its reach since then, Rails (and, by extension, web dev) so dominates the conversation in that community that many people unconsciously forget it's a general-purpose language and are often unaware that there are libraries out there for doing non-web work in Ruby. Python's early advantage for scientific stuff was its relative simplicity and its easy integration with extensions written in compiled languages. Interpreted languages will probably never be fast enough on their own for scientific computing, but a high-level interpreted language as an interface to fast compiled C and Fortran is good enough to attract people and introduce network effects which turn a moderate advantage into a big one.