Despite Steam making all CD keys obsolete for Valve games over a decade ago, the search persists for three reasons:
Major gaming history YouTubers (like Nostalgia Nerd or LGR) have featured CS 1.1 installs, driving up the search volume. When they show the "Enter CD Key" screen, thousands of viewers rush to Google to try and replicate the experience. cd key cs 1.1
This is for the purist who wants the original installer. Despite Steam making all CD keys obsolete for