Excluding school projects and toy languages, who here has created a programming language and why?
I'll go first. 13 years ago I created a specialized language for processing XML data. XmlPl marries the syntax of C, XML and XPath. It is very fast and efficient. It never caught on. See http://xmlpl.org.
Despite being a modest, fun experiment in stripping JavaScript down to a minimal skin, and without any corporate backing, it wound up catching on a little bit.
Thanks to the hard work of Geoffrey Booth and Simon Lydell, among others, there's a new "V2" version that includes many ES6 and 7 features that's almost ready to go: http://coffeescript.org/v2/
CoffeeScript was designed extremely conservatively. The goal was to stick close to JavaScript semantics, to avoid having a runtime, and to avoid features that would require gymnastics and overcomplications in the output, or would run noticeably slower than the raw JS equivalent.
These days, I'm most interested in trying something from the other end of the "political" spectrum: What would happen if you tried to make a web language that wanted to strip HTML, CSS and JavaScript down to their essence — but were extremely liberal in the techniques you used to get there?
I'd like to get a chance to give that a try some day.