Why would you use a scope when you could use regular Ruby class methods?

Scopes

class Comment < ActiveRecord::Base
  scope :most_recent, -> (limit) { order("created_at desc").limit(limit) }
end

using scope

@recent_comments = Comment.most_recent(5)

Class Methods

In Model

def self.most_recent(limit)
  order("created_at desc").limit(limit)
end

In controller

@recent_comments = Comment.most_recent(5)

Why would you use a scope when you could use regular Ruby class methods?