Perfect fit baby clothes

Why do childrens clothes come sized in one dimension (e.g. 0-3 months) when children come sized in at least 2 dimensions (length and weight)? It would be cool to have a subscription service that asks you to select clothes and weekly fill in your childs lenght and weigh and then sends you clothes *that fit*, for the correct season one or two times a month. I think that many parents would appreciate perfect fit clothes for their children, with little effort and at affordable prices.