I'm glad to see I'm not alone! I also had ~/Work.MD stored for the past few years. Each day I add the date as a new top-level heading, and write notes of what I did.
I've recently started contracting (and billing hourly) so I've switched to using an org-mode file, which contains commands, links to internal stories, and other things.
As I'm contracting I figured I might be asked to justify the hours-billed, etc. So for the first time I'm explicitly writing the daily-log with the expectation that I'll share it, and the employer will see what I write.
That (perceived) level of scrutiny has really improved the detail and coverage of what I document.