Because typing is an act of commission, not omission. Clicking a box is passive; you do it a hundred times a day for software updates and cookie policies you never read. But forcing the user to manually type "CS RIN" is a deliberate cognitive speed bump. It forces a moment of reflection.
It is the digital equivalent of signing a blood oath with a quill. The capitalization matters. The space matters. The lack of a period matters. It is a shibboleth—a linguistic password that separates the curious tourist from the committed pirate. Of course, the profound irony is not lost on the denizens of CS.RIN. You are agreeing to their terms in order to violate someone else's terms (namely, Valve's Steam Subscriber Agreement). cs rin i agree to these terms
In that moment, the forum is saying: "You are about to enter a place where Steam manifests don't matter, where licenses are suggestions, and where a single mis-post will get you exiled. Look at the letters. Accept the risk." Because typing is an act of commission, not omission