No follow links exist because we dont want every single webpage or link to be something a search engine crwals and ranks.Therfore no follow link attributes tells search engine bots not to follow a certain link.The link is still a clickable for a user,but not followed by a bot.
On the other hand all other links could be considered do follow links even though they dont have to have special attributes to tell the search engine bots to follow them the bots will by default.