No, it's absolutely not necessary to cook on a tour. It goes against the grain, but I haven't carried a stove or cookset on a tour or hike for many seasons. It doesn't give you a huge weight advantage because there are many very good light-weight stoves, and you have to carry more water weight in the food. But it does make things simpler and easier to resupply. Another advantage is pack space--I dropped an entire front pack from my set-up when I stopped carrying a stove. (The other front pack got dropped when I found a decent single-wall tent (Henry Shires Tarptent).)