As for paper sacks...I haven't seen one in a store for years. I am using the cloth bags now, and trying not to have to rely on the plastic ones that most of the stores have now. I still end up with some, but not near as much.
Most of the stores I go to have a choice of paper or plastic. I bring my own (when I'm clever enough to remember) which I store in the back of my car for convenience -when I remember to put them back there. Time to feed the chickens...
When I can find them, I like to use large paper bags to trace pattern pieces for my sewing projects rather than cut up the store-bought patterns (they can be so expensive and this extends their usefulness.)
I transfer the markings to the brown paper and make sure I right the pattern piece size, number and various notations about which direction the grain of the fabric should go, etc. and keep the original patterns uncut and folded nicely back into the package.
For patterns that can be used for several people, I make whole pattern sets out of paper and keep them bagged up together in Ziplocks with the person's name and date, so as to keep all the fiddly pieces straight and well-organized.
Also: I use a brown paper bag under the sink to keep compostable scraps from the kitchen, and when it gets full enough, I roll it up and toss it on the compost heap. Easy!
Those paper bags are becoming rare, but I try to put them to good use whenever I get my hands on them!
ripening avocados
wrapping gifts
drying herbs upside down(they keep the dust and light off of them while they dry)
customers to carry off soap
patterns
drying seed
as a grease mat for fried foods
trash bags