The reason is simple: we're short, our legs are short, we like them, we like the sound of the heels while we walk, we feel prettier, we want a heels collection, we need them in all colors, we need a pair for december , another for april mer and an intermediate one too, we want to have them in different textures, we have a fetish with shoes.
From the simpliest reason to the most extreme one, we can't deny high-heels are never going to be out of trend so it's a good investment (well, that's what I like to say to my boyfriend even if he doesn't ask). Take care of your feet with cream, exfoliation and adhesive bandages. And let's thank fashion for wedges, flats and sandals :)
Also, after reading about this woman who owns more than 1,200 pairs of shoes (700 of them are Louboutin) I cannot feel bad about spending on shoes!