Because I work with data pretty often, and working with data pretty much requires a monospace font, and there's no reason for me to switch back and forth. For

Because I work with data pretty often, and working with data pretty much requires a monospace font, and there's no reason for me to switch back and forth. For example, cli mysql wouldn't be too much fun in Geneva. There's a nice visual hint between labels and data in lines of whois output, and that hint would be icky in a proportional typeface: status: reallocated owner: NETLINE PERU ownerid: PE-NEPE4-LACNIC Also, log files with columns like timestamp [ip] etc., and some particularly friendly configuration files. And, although it's not very common, I occasionally use it as a typo-checker. If I have a function or a class where I can't easily abstract out some kind of repetition, then using a monospaced font with variables that are the same number of characters lets me visually see right away if I've mistyped something. I couldn't quickly find an example, but it was the first programming-specific monospace font thing that came to mind.