Added a bit to the game having to watch how many spells I had left and how many camps I could set before having to head back.
A lot of the time I ran into extra camping supplies and made it a pretty far way without having to return to a vendor but there are areas where you will have to oblige, quit your mission and go stock up. It's a mechanic of the game that works and does add that slight layer of "difficulty", or tedium might be a better word. It's not like the enemies will respawn and you have to fight back through them. It only makes it so you can use up your spells and some actions, so it isn't quite as easy to plow through the game. The mage would be ridiculously overpowered if you could just spam your strongest attacks on everyone over and over. So now you have to manage them and who deserves the strongest.
And yes, camping supplies would be used up after one use; firewood, food, tinder, etc.
cavemandiary is right.
Theurgist, no offense but the way your complaining sounds like you'd be happier just button mashing mage attacks over and over? All I can imagine removing the mechanic would accomplish is cutting a few hours out of the game. It's already short enough.