Comment by jherdman

Composability is the often cited benefit. As an example, I can do the following in Active Record (Ruby):

  class Account < ApplicationRecord
    scope :active, -> { where.not(active_at: nil) }

    belongs_to :user
  end

  class User < ApplicationRecord
    scope :born_before, ->(born_on) { where(birthdate: born_on) }
  end

  active_users_with_birthdays_today = Account.active.joins(:user).merge(User.born_before(Date.today))

Contrived, of course, but it's not hard to see how you can use these sorts of things to build up record sorting, filtering, etc. Doing this by hand wouldn't be very fun.