I asked myself the same question
it's too hot where I live (Texas) right now for Rasta to wear clothing comfortably, but when the temp starts dropping to the 60's I'll put little sweaters/jackets on him to keep him warm(yorkies dont have an undercoat to keep them warm). Now as for the hairbows and neck ties I put on him...they have no "real" function I just think they're really cute