Because unattended camp fires cause forest fires.
Propane camp stoves just don't have that track record.
You might also note many places prohibit smoking too, for the same reason.

There is a fire risk, but it is much more than that.

Simply building a fire ring is against "Leave no trace" ethics. And outside of a campground, no one, it seams, is happy with the fire rings left by others and people seem inclined to build their own. Some can be ridiculously large too.

The fire rings in turn evolve into garbage pits. A paper plate or napkin is easily consumed, but they are often default garbage dumps for tin cans, foil, beer and pop cans/glasses etc.

Fuel is also an issue. Just a few fires can leave naturally dead and fallen fuel depleted in the area. From there people tear branches off of living trees, or use the wood from fences, tables, signs, etc. Even a dead standing tree can be animal habitat and falling the tree is a safety hazard, and is usually unlawful in a park setting, but mostly it is unethical in the context of "leave no trace".

The good news for you is there are stoves designed to run on a very small amount of debris including wood, grass, even dried dung. These are normally allowed even when open fires are not. The simple charcoal grill is also normally allowed. I have grilled nice steaks on a charcoal grill made from a larger coffee can, small chunk of wire mesh and 10-12 standard briquettes of charcoal. I would not do this on one of my longer hikes, but have carried this type of grill for 10-12 miles.

Here is a commercial wood stove of high quality. There are numerous resources on-line to build similar devises:

http://www.zzst…

EDIT: I hope "J" returns and notices this, he is correct in the stupidity assessment. In 1988, the last year I fought fire, and while several thousand acres were burning in Lowman, Idaho, I checked a dispersed campsite where I had earlier seen a large RV parked. The RV was gone and a circle about 20' in diameter was actively burning from the fire-pit. This idiot was within sight of the smoke and flames of a major forest fire and STILL managed to neglect his own fire.

I'm in the US and we have very similar regulations in many camping areas. The reason is to prevent forest fires. Many people do not understand how to properly extinguish a camp fire. This seems like a very simple task but I've seen coals that are two days old. This is after campers poured water on their fire and moved on.

Campfires that burn longer and hotter heat the rocks and create coals that sometimes sit deep under the fire. The campfire not only needs to have water thrown on it it should be covered in dirt. One time I came across an abandoned smoldering campfire that was clearly doused with water at least one day before I found it. We moved the rocks around a bit and the red hot coals were visible. Very near the fire ring was a dry fir tree. With a couple more days, a little bit of wind and a branch the entire forest could have easily caught on fire. Until that point I had no idea that a campfire could survive being drenched with water.

While one could easily tip over a gas stove and set the forest floor on fire, at least we know that once the stove is turned off it is off. There are no coals.

I prefer campfires personally and wish we didn't have to require gas stoves. I agree it does suck.

you can't underestimate the stupidity of some campers. more than once i've passed by still-red-hot coals in a fire, directly under a tree, where the campers have already packed up and left (yes, i put the fires out myself).

a smaller reason but additional to what's been mentioned, it can be a benefit to banning open fires so that campers don't bring in their own wood. sometimes campers will bring in their own firewood and inadvertently spread wood diseases and harmful insects across the area.

allowing campfires also goes a way to deforesting an area. any and all fallen wood will get picked up by campers coming through (hurting regrowth), and campers will also start tearing down younger trees and bigger tree limbs to make their fires.

Gas stoves are actually fairly simple tech. I like to leave the gadgets at home mostly, but I like camping stoves. A few advantages:

1. They have a lower immediate impact on the area. You aren't disturbing wandering through the brush looking for wood, nor do you leave behind a pile of ash and fire ring. With a gas stove, you leave the site the way you found it.

2. I find I can travel further and longer when using a gas stove. Gather wood for a fire can take up valuable daylight time that I could use for either traveling or relaxing. You have to carry a small bit of extra weight, but I think it's a valuable trade off.

Here's the simple answer. Gas stoves are more easily and readily controlled and don't produce the flying sparks and cinders that campfires produce.