How did this roll out without some kind of filter? Valve you used to be smarter than this.
Oh, it has a profanity filter. No 'Penis Brotherhood' tag for Rust. I think I like it better that way, no advanced warning for new people.
Because you need enough data to determine what is meaningful and what is not. For example the term "gay" could actually be a genuine tag but is quite likely to be used in a derogatory manner. So you need to collect enough data to the determine how to filter and weight certain terms. There will no doubt also be a number of terms/swears that go under the radar, notable a bunch of racial slurs and English phonetic translations of foreign swears i'd guess
Ultimately, the most meaningful system will be one where the community is able to express itself in a way that is as unrestricted as possible, thats gonna need a fair amount of data collection to begin with much like when last.fm started tagging