The wife and I have different priorities for what we carry,even hiking together.I use water bottles for day hikes and need an accessible bottle without removing the pack..the same with a smaller digital camera,some trail mix,and other smaller items I don't care to remove a pack to acquire from it.Some packs are impossible to reach a water bottle,unless you are a contortionist.I don't care for the taste of hydration bladders..and usually carry juice,margarita mix(ed), or iced tea/coffee instead of water..other reasons the bladder doesn't work well for me for day hikes.
I also prefer equipment straps down the front of the shoulder straps for clipping on
a small knife,firestarter,p38 can opener,goat spray,and other small easy to lose and hard to find items once in the bottom of a pack.A smaller back pocket like the R20 is handy..verses not having one on the R8..especially for the wife with her cell phone,small personal items,FAK, and benadryl for emergencies for bee stings.Some things you do not want to search for.
We do have a couple torso packs that convert to full height day packs(pacific crest and kelty)..which weigh less than 1lb.The top area always stays up with the shoulder straps,never used as a torso pack..room for jackets,raingear,and other lightweight items besides extra water or juice in bottles,lunch,and other larger, lighter items.I've added more straps across the exterior sides and back for more equipment outside the few times we need it..or drying wet jackets,packing sandy beach shoes,etc.A little strapping,small caribiners, may add a whole ounce or two but comes in very handy.
I have yet to find a decent day pack with everything I require and still maintain that 1lb limit I require also.My revised torso one comes pretty close.Unfortunately the Pacific Crest(labelled)company went out of business or I'd be buying three more.It doesn't feel like you are packing anything at all.
I don't generally carry a lot of survival gear but pack the basics for the better weather I normally hike in(tarp,warm clothes) and need a lower(below waist) pocket for food and cooking gear..but I do pack enough to survive a night in the woods somewhat comfortably if needed.Cooking on day hikes at the most can be noodles, coffee press/pot,and maybe even a baked dessert(local berries in season)..and I normally carry enough fuel for 3-4 meals(say 8-10oz heet..outside mesh pocket that doesn't have a water bottle)along with a 2oz stove,ziploc insulated pot,etc...even if we plan only one meal.
Waist belt pockets..end up carrying toilet paper,extra socks,or other "padding" items..so I hope they didn't waste weight by adding padding there.Most day packs don't even need waist belts..but something very lightweight and simple works for adding a small camera bag.Lately I've been using a "pet treats" bag for packing a camera.the top has a drawstring with a cordlock..ever since a velcroed LowePro one dumped my good digital in the sand..
The doggy treat ones work great for powerbars,trailmix,and jerky also...I don't need the dog.
Occasionally I carry a water bottle up on the front shoulder straps equipment loops with a neck noose for the bottle and a cordlock/bungee on the lower portion to stop sway..That works fine,weighs nothing,and easy/quick for access.
Some omitted necessities on day packs can be overcome with lightweight ingenuity...
As I said,I have yet to see a daypack with everything I need and am not afraid to modify one to fit MY
JJ..that's in the area around Seattle and the ONP/Coastal areas..so I know what conditions you are in also..similar ones.