Why can't puppies come already house trained?

Aaaaarrrggggghhhhh Alfie has been a nightmare today, it is like he has forgotten EVERYTHING! We are trying to train him to go the toilet outside and we were doing really well but that all went out of the window today! He has had about 8 wees on the kitchen floor despite being put outside regularly. It is as though he just can't be bothered today- it is very frustrating as you feel like you are getting somewhere and then it is back to square one! I want him to be trained as quickly as possible as I am having to work in the kitchen at the moment which is pretty annoying but there is no way he is ready to be let loose on the carpets yet!