I live in Denmark, so the short answer is that I don't. Big-o came up in an interview once, but it was mainly along the lines of being asked if I knew what it was and me answering with a yes.

I've spent a semester doing all sorts of silly algorithms, including * sort, so it's not like I couldn't handle them if it was ever required. The thing is, time to market and code consistency will almost always leave you using the standard libraries which came with your environment.

There are obviously a few jobs where it's relevant, but I'm into things like architecture, digitizations and business development, so I'll never work one of those jobs, and neither will 95% of you.