No reason at all. Just remember to use good thread when you do any stitching.

Along with nylon canvas and the like, you might want to look at Tyvek. You can buy it in rolls that are something like eight or nine feet wide, and it will pack a lot smaller and lighter than any kind of canvas. But it probably won't take the beating. It's also plain, glossy white, so it will stick out like a sore thumb so long as it isn't in snow.