Interesting… I got the retail version back then and it was bundled with Steam and did check your account on every start (or required a steam client running with the title in the library). It even had a warning label on the box stating that it needed a steam account and that the CD key would be linked to your account. But I do not remember it using Securom. Which checks out, as I vaguely remember buying I after Christmas.

Maybe it got removed later? I can find some discussions in the steam forums arguing about the drm from about 10 years ago, and other more recent discussion where people are wondering why it has no more drm - e.g. this comment describing the same procedure as I did above

Fun fact: My Steam accounts lists that it was created in July 31st 2004, although Steam was released on September 12th 2004. I guess they just added a random date on old accounts that didn’t have a date registered?