The liners are reusable for practically forever, so they can be a good investment for a person living in a thorn-infested area, or commuting on glass-strewn streets or bike lanes.
I'm blessed with an area where there aren't many thorns, so I don't (I primarily get pinch flats, from going too fast across rocks). I'm a weight weenie in remission, but I still can't bring myself to add the extra weight to the edge of my wheels.
Thorn-resistant tubes are another possibility; a bit less puncture resistance but very resistant to pinch flats. For a rider who gets a few thorn punctures from small thorns, and pinch flats as well, they could be worth a try.