If you are just trail hiking, even for a couple weeks, with cheap gear that isn't "ultra" light one doesn't need a big pack.
That being said. My first pack was a 4.5lb external frame pack. Loved it after it quit squeeking on milepost 8 or so… digging into my back with its cross bar, smacked my head with its top bar…
Also have used a Kelty Super Tioga at 8lbs to carry 4×5 view cameras with all the film slides, change bag, light meter, etc. It adds up fast and takes up a Huge volume of space.
For weekend take a 2000 cub inch pack.
Bought Dana Designs Astraplane online because it was going for nearly free and then decided that the Gregory Denali Pro was better for hauling 4 weeks of food and climbing gear for going into remote locations in the Coast Mountains of British COlumbia. These packs are deficient at any load over 70lbs though. Dana Designs/Gregory/Arc TEryx/Osprey are all the same just different colors really and price.
Even for carrying only 50lbs of climbing gear for a week-10+ day trips through the pickets in Washington State North Cascades National Park MChale packs are still superior to a 55L black diamond pack which is darned good as it has haul loops and ability to attach a bunch of gear on the outside which I have used extensively for climbing for week long trips. Mchale packs shrink for doing rock climbing as well.
If I had tons of money, sure I would buy all super light gear and get a dyneema McHale backpack. Real reason? I carry a lot of photgraphic gear along with my climbing gear. Better to be comfortable than miserable.
IF like most folks the longest you go out for is 3 days, then no one needs a large pack. If you have to haul other peoples crap, cuz they are newbies, or because you want to go somewhere remote, then you need the big pack. Or you are one of those folks that MUST stick everything inside your pack making it impossible to find, requiring a 5 hour stop everytime you want a snack…