Sigh... you really don't understand how much preliminary knowledge and prerequisites it takes to "simply" issue that command. With this answer you demonstrate exactly the mindset why so much information is behind some obscure knowledge and pointlessly so. "I know it's there means others know it's there" sigh...
Not to mention that ~95% of the Earth's population doesn't speak English as the first language, how stuff is named in English is not obvious. Bad search engines, like what `man -k` has, are nearly unusable if you don't know the exact term. You'd laugh when people would recommend to you to look up words using a paper dictionary or write papers using paper encyclopedias but `man -k` is pretty much that.