For travel, I have some small largely pre-packed kits that I throw in my carryon. I revisit the contents from time to time and I may adjust my electronics charger/cable kit if e.g. I have international travel. But for the most part, I find having a kit with spare glasses, first aid kit, a few sometimes needed/wanted over the counter meds and lotions, etc. is worth a pound or two to just have self-contained that I can just grab.

And certainly for group hikes for example, I carry a much larger first aid kit than I have any expectation of needing but I hopefully have the appropriate items if I need them.