There is no weight savings because the small amount of weight that is saved in tubing is made up for by the longer and usually heavier seat post. While true compact frames do save on inventory by requiring fewer sizes, there are many frames made today that have slanted top tubes, but are not technically compact. They come in about as many sizes as standard geometry bikes. A good example is the Trek Madone series. It is now more about style than anything. Kids just like the look.