*Availability, time, money, no shipping, design (they don't work well in freestanding applications IME ... ie, work better when applied to a frame/structure) *All these types of bendable sheet goods look great on the Internet, but just try to find someone that carries them locally and has them "in stock", even in one of the largest urban areas in the country. If you do find it, it is always 3/8" and any other size must be "$pecial order".
And, it's why I have the tools to do the job. :)