this was probably 25 years ago -

I started collecting chips after visiting several casinos and acquiring trading stock

I arranged a trade with an older collector who advertised a lot of cool items on one of the early chat rooms - maybe Chequers?

Anyway, I had only been to a few casinos, so I didn't have 10 different chips to trade. I offered to trade 10 from some remote northern Michigan casino, and he said okay. I confirmed that he would be getting 10 chips from the same casino, and he confirmed.

A week later, he complained that I had sent him 10 identical chips. That left a sour taste and I turned my attention to buying chips instead.

As for a recent decline in trading, I suggest postage costs and "I only need the rare stuff now" would be typical reasons.