If it weren't for significant pack lightening, I would no longer be backpacking! Lightening up has enabled me to keep going into my 70's. However, there are some creature comforts (such as a 2.5" thick sleeping pad) that this old gal can't do without. My current base weight is 12 lbs., although this includes some items often eliminated from gear lists, such as camera and fishing gear. I guess that puts me on the verge of UL, but not quite there. It's close enough for me, though!
For quite a while, lightening up meant I could go out for the weekend with half the pack weight I used to carry in the 1980's. More recently, I've eliminated more gear weight so I can go out on longer trips (8-10 days) without resupply. I suspect, though that as the years go on, I'll be taking shorter and shorter trips. Not only am I not getting any younger, but per the vet my dog is now a "senior dog." A 15-lb. total pack weight for an overnighter, though, will let me keep going as long as I (and the dog) can put one foot in front of another, which is what I plan to do!
It's really an individual thing. For some, lightening up most of the pack allows a few luxuries to be carried, such as chairs, without significant burden. Or, as with me, being able to lengthen trips and still be comfortable. Or, carrying lots of heavy photo gear. For some, the accomplishment of surviving with a sub-5-pound pack is most important. We can all learn a lot from the UL, SUL and XSUL folks even if we don't imitate them completely.
All hail, the concepts of HYOH and YMMV!