As some others have pointed out, speed of the application at runtime is not always the most important consideration, else we'd probably be doing everything in a mix of Fortran, C, and Assembly.
I have found that developer productivity is higher, especially when it comes to maintenance. For me, all the tools in an IDE help offset Python or Ruby's simplicity when working in say, Java, when writing new code. But when reasoning about old code I haven't touched in a while, or looking at others' code, Python is easier for me to reason about.
If casting about for a reason to learn any new language, I can think of a few. Understanding another language and how you approach problems with it may provide insight on how to better use your main language. Your career may be long, and your main language may not be popular forever. When acting as a hiring manager, I look for people who know multiple languages, even if I only need one. Especially if they tackled learning them outside of school. It shows both passion and initiative.
I have found that developer productivity is higher, especially when it comes to maintenance. For me, all the tools in an IDE help offset Python or Ruby's simplicity when working in say, Java, when writing new code. But when reasoning about old code I haven't touched in a while, or looking at others' code, Python is easier for me to reason about.
If casting about for a reason to learn any new language, I can think of a few. Understanding another language and how you approach problems with it may provide insight on how to better use your main language. Your career may be long, and your main language may not be popular forever. When acting as a hiring manager, I look for people who know multiple languages, even if I only need one. Especially if they tackled learning them outside of school. It shows both passion and initiative.