Well that's like asking why you have more than one shirt, one pair of pants, one pair of socks. You only have one body, so it's logical that you'll only need one article of clothing for it. However, clothes get smelly and need to be washed and sometimes people grow out of them or they start falling apart, but that's not necessarily the same with shoes. I live in a state where it's ungodly hot in the summer and snowing in the winter. So am I only allowed to have snow boots and a pair of flip flops? Or is it ok that I have sneakers to go jogging in and high heels to wear when I go out on dates? And what about my husband who has two different pairs of shoes just for his job?
Not all women need ten pairs of shoes, but the same way you have ten shirts that aren't all the same color or design, women have ten pairs of shoes for different occasions and outfits. A pair of red pumps shouldn't be worn with a green blazer and business skirt and they're definitely not office-friendly. The exact same way a cut off t-shirt isn't appropriate for a CEO to wear to work or for anyone to wear into a fancy restaurant.
Shoes, like clothes, are an accessory. Men might be happy with one or two pairs, but that's the difference between the genders: we're a chromosome apart. Maybe the need for shoes rests on that extra X.