I didn't the first 10 years. Then the projects needed more coordination (team members), more refactoring, future proofing (making sure one can replace individual parts), dealing with external API and simply having had to deal with too many complex bugs. Apart from very visual projects (HTML layout), all libraries, especially open source, I add some tests.

It's usually not 100% TDD: I write code first code, then tests in parallel or shortly after. Striving for 100% test coverage (there are tools for various programming languages) is hard. Only very rare do I write test first, then code. That would require specification from somebody, or e.g. dealing with an external API.