Because of the existing code and libraries which are not available in other languages. For instance if I am writing some NLP related code I would write it in python.
Ironically, that'd still be better than JRE, because your NLP libs end up spending most of their time in high performance, memory efficient C++ code that underpins such libs.
No man I wouldn't want to call those horrific c functions compared to those sweet python functions ! and the libs calling those C functions do much more than just being a wrapper. they add a lot of tooling around.