this is actually an old Unix Sys Admin "joke", as quite often you might type "rm -rf ./*" (i.e. remove everything below the current directory), but if you miss the "." it wipes everything off the filesystem.

Hence, experienced admins developed methods of avoiding situations of having to type that type of thing due to having at least once accidentally done it themselves.
The most common reason for having to type this, was to remove some software.