[dkopi]

While true that some languages (and supporting open source modules) are better at certain tasks than other, I believe the real reason people want "one language to rule them all" is reduce the loss in productivity due to context switching between languages.

Try going back and forth between langauges when you have an app in Java/Obj-C, high performance native code in C++, a backend server written in python/php and an admin dashboard written in Javascript.