lets see... what do you think all the people play with ... do you erally think they all use linux? no. i bet at least 90% are using windows xp (plus a few % using windows 9.x or nt/2000 so we're at ~98%). ok, now since we know they are all playing with windows.... lets see what do they use to play.
hmm .... won is down... what else can you use to play halflife / hl mods online .... STEAM
conclusion: the 1.2 / 1.2.1 versions were MADE for steam.
 or if you were asking where to get a (windows) steam version ... check the post above :O