Contrary to what many think, ultralight backpacking is not just about the freedom to hike more miles or to take your whole pack up the mountain with you. It is also about comfort and safety. Backpackers with heavy loads work too hard and threaten their joints too much. Challenges may add to the experience, but why suffer more than is necessary?
You can't easily take a side trip up that hill, just to see what is there. If you do it without your pack, you have to go back the same way to get your pack.
Putting on and taking off your heavy pack quickly becomes a chore. You start leaving it on even during rest stops, just so you don't have to deal with it.
Backpacking is clearly more tiring with a heavy pack, and you probably won't enjoy yourself as much when you are tired.
Sprained ankles, blistered feet, sore muscles, and back and knee problems are just some of the common consequences of too much weight on your back.
More weight equals slower progress, which means less access to wild places (you can't go as far on your four-day trip), or it means less time to for enjoyable activities, like a swim in a mountain lake, or a relaxing evening in camp.
More injuries, and the inability to move quickly when a storm is coming or an emergency requires you to get to a road, means that backpacking can actually be more dangerous with a heavy load. Add to that the possibility of bad decisions due to tiredness.
Done the right way, ultralight backpacking gives you more freedom, more comfort, more safety, more enjoyment and less suffering than traditional backpacking. It allows you to move faster, but notice that I say "allows." It doesn't require it. It just gives you the option. That's more freedom.
I have yet to meet or hear about a person who has tried lightweight backpacking for a while, and then gone back to a heavy load. I'm not saying it is for everyone. Bad ankles may require heavy hiking boots, and bad habits may require a big pack to satisfy them. But even a backpacker who needs a pillow and big rectangular sleeping bag, can find these in lighter forms.
You just can't understand the sense of liberation felt by a convert to ultralight backpacking, until you try it yourself. When I, with my eleven-pound pack, walk past overloaded backpackers struggling up steep trails, I remembered being in their place, and I know I am enjoying myself more now.
Not so. Bring your favorite camera! A lighter load means you can stop to use it more easily. If you leave behind the things you don't need, and bring a lighter backpack, tent, and sleeping bag, you can more easily bring that telephoto lense or whatever is really important to you.
The opposite! Bring all the safety items; a sleeping bag, first aid kit, shelter, water purification, etc. Just bring lighter versions. A light load makes you less likely to lose your balance and fall, or to otherwise injure yourself. It also means faster response to iffy situations.
A note about safety:
It is lagely a matter of knowledge and experience. A trained survivalist will always be safer backpacking with no shelter than a neophyte with the best tent. Learn a little about how to use you equipment properly, or to read the sky for comimg storms, and you can go lighter and safer.
Is it less comfortable to have 18 pounds on your back than 50? Is it less comfortable to have an ultralight sleeping bag if it keeps you just as warm? I stopped getting blisters (totally) when I started using running shoes instead of hiking boots. Cut the weight on your back by twenty-five pounds, and you can add back a heavier coat, if that is what you need to be comfortable.
Ultralight sleeping bags are expensive. Almost everything else needed for ultralight backpacking can be found for the same price or cheaper than traditional gear. There are many sub-three-pound backpacks under a hundred dollars, for example.
Try it. The first time you are fifteen miles into the day, and you realize that you can easily run up that hill-just to see what is there, you'll know you made the right decision.
Steve Gillman is a long-time backpacker, and advocate of going light. His advice and stories can be found at The Ultralight Backpacking Site. (http://www.the-ultralight-site.com)