Just left of normal

At work (a large well known bookstore which i can not disclose for legal reasons) i was standing around trying not to continuously bug the 2 whole customers in my department. And on our lovely Gaiam gondola there is a wealth of yoga mats in every color and shape, some are shorter, or thicker, or wider there is even a 'light weight travel mat'. And looking at them i was wondering do you really need a mat to do yoga? I mean unless you are on a tile floor, or maybe a sidewalk... isn't the floor/ground soft enough? Really, i was honestly contemplating getting one then i stopped myself and wondered why, do i really need this. Maybe its just a "grown-up" version of the kindergarten carpet squares "Spread out so when you stretch out your arms you don't phack your neighbor. If you can touch the person next to you, your to close."

Or maybe there is an actual reason - that i am just completely unaware of and totally ignorant on the subject. If so, someone correct me. Despite this for whatever reason i still want to get a yoga mat, but since i don't really have the money to blow right now and i don't know what it's actually for i've decided on this... I've been wanting to make the Namaste Knitty pattern for some time though you can see why i didn't have occasion to knit it before. My plan is that if i knit myself a Namaste -to completion- (who knows how long that maybe, if ever) then i will reward myself with a yoga mat to put in it.

So REALLY... does anyone know why we have to have a mat for yoga??