Because that's actually from a demo, called Half-Life: Uplink!
Here, I found a video with that exact location: http://www.youtube.com/watch?v=bLLBnkCmgZ8&feature=player_detailpage#t=412
ah that makes sense, although I've only played HL1 like once.
Really MRORANGE
Next you're going to laugh at me for not playing System Shock 2.