Registering any of these boxed games on Steam got you access to all of them: HL, Opposing Force, Blue Shift, Counter-Strike, Team Fortress Classic. + some Valve made mods: Quake DM, and Ricochet.

That's a pretty good "carrot" to use Steam if you ask me.

That may have changed after I got steam.

I only had Half Life, and Counter Strike was free when I started playing so I only got HL / CS. I didn't get the others free until HL2 came out...

This is what you should have got with any retail HL CD key:

https://steamdb.info/sub/1/apps/

I can confirm it worked with HL1, CS Retail and Blue Shift keys.

Still waiting for Ricochet VR.