Thanks!, I had not seen the style guide. As someone else said, this probably comes from Google’s purchase of ITA. Common Lisp is stable, well documented, many fine implementations so I find it odd that there are only pockets of developers/companies who use it. Similar situation with Haskell.

It is definitely curious. Whenever I mention Common Lisp is my preferred language people start talking to me as if I'm some wizard from another dimension. That, or stupid parenthesis jokes.

It really has an image problem.

I always try to explain that I like Common Lisp because it is an easy and very practical language, but the people I talk to that have no experience in it think it is very hard and impractical. I think the latter is because of university courses where one is not allowed to use the full power of the language.

Low popularity, meaning it's much more difficult to find employees proficient in it, making it a bad proposition for companies... which keeps it unpopular. The vicious cycle of fashion.

If such vicious cycles were true no new programming language would gain adoption; after all even Java was "a new language" at some point of time.

What Java helped was the big pockets of SUN / later Oracle, because it was their language. Initially for small machines, it then helped them to sell lots of hardware into the 'enterprise' running slow (but portable) Java applications.

That guide is mostly what the reservation system used (now canceled). At the time of the merger QPX (the flight search) was ... diversely styled.

The Lisp Style Guide actually predates Google's acquisition of ITA. Common Lisp was used to develop some machine learning code. After the acquisition of ITA, the guide was extensively updated.