Some enthusiasts like to try to collect sets/series of weighted chips because they are older and therefore rarer. The better condition chips maintain their weight. Heavily used chips will have lost a bit.
Back in the day, I was fairly regular on the Admiral. Lots of fun stories in the poker "room/rooms". One evening I showed up and they for some reason had introduced quite a few new $1s. Just the poker room cage as far as I know. I always collected $1s and a bunch from Vegas and I am pretty sure I filled a rack with 50 - $1s and 50 - .50 cents. They're in a tote in the basement so I'll have to check to remember exactly what I have.
Side note, back then they only spread 1-4,4-8 spread limit and 15/30 or 20/40 limit. There was also a $500 loss limit every 2 hours so it was not unusual to carry $100s or "pumpkins" home every night. If someone went busto and there 2 hours wasn't up we would pass chips and hundred dollar bills, literally "under the table".