PROGRAMMERS NEED TO COMMUNICATE. A lot. There are periods in a programmer's life when most communication seems to be with the computer—more precisely, with the programs running on that computer. This communication is about expressing ideas in a machine-readable way
Programmers need to be fluent in the language of the machine, whether real or virtual, and in the abstractions that can be related to that language via development tools.
Beyond communication with machines, programmers need to communicate with their peers.
Beyond communication with machine, self, and peers, a project has many stakeholders, most with a different or no technical background.
Programmers are ultimately responsible for bringing the ideas to life via a computer.
to know another language is to have another soul. For your contacts beyond the software industry, you will appreciate knowing foreign languages.