i day hike year round in the southern california mountains.

i have asked myself the exact same question on many occasions, especially when i see - as you describe - those that aren't prepared for much of anything.

in the summer, as the temps get into the 80s - 90s - and 100s, i carry a pack with two 100 oz camelback bags. so i start @ over 13 lbs. the pack is 1 1/2lbs. so i guess i'm really starting @ about 15. let's add the heatsheet, cell phone, knife, leatherman, headlight, gloves, compact saw, bag of tricks, extra socks, shirt and lightweight jacket, and oh yeah, food, and i think i'm in the 20 to 25lb range. easy.

i figure i have enough to spend a semi-comfortable night in the woods, if need be.

i'm sure i could pare some of the weight, but in the grand scheme of things a pound or two doesn't make a big difference to me while dayhiking - but it does bring peace of mind.

one lesson i learned from my hiking buddy was how to pace myself while hiking. with a cup of coffee in the a.m. i was all ready to let 'er rip. and found myself gasping as well.. now, we don't mosey along, but we have started to have a slower step pace - and find that we have the same elapsed times as previously on the hikes, but arrive not so worn out.

we try to really pace ourselves as we typically look for peaks or mountains to summit - and when you're on the summit you are only half way there. i've read many accidents occur late in the day when you're tired - so we try to pace ourselves for the long haul. and so far, no accidents.

i also find that going to a fitness center for about an hour after work every day makes a difference too. for the most part i sit at a desk. sluggo. i doubt i could do the 8 - 10 hr, 15 - 20 mile, 4,000' elevation gain hikes as easily w/o any in-between exercise.

whew, next time i'll try the reader's digest condensed version.

but i hope this helped!