Python is one the most popular programming languages. Ruby fits into a similar category as Python (high level, interpreted scripting language, very dynamic, has a rich ecosystem with tons of existing code). Being faster than Python makes it more attractive to use, or port Python codebases to.
And with Java, and with Go, and with Rust, and with pretty much any language offering some form of FFI.
But they're used with Python, and good luck convincing your interviewer that it should be used with Ruby.