Which is why you don’t have physical copies of those games - you bought a steam key, exactly like you could have done digitally from humblebundle of greenmangaming or myriad of other stores, this one just had it printed on a piece of paper instead of sending you an email.
A Steam key Valve didn’t get a cut from, btw.
Helped you (and Valve) to save some bandwidth. But yes. If it requires a Steam account to play, you bought a license allowing you to access a game using Steam, and not an actual game you own.