I collected S&H trading stamps as a child so I had a little clue about loyalty programs.

In the 1970's Swissair had a program called Swiss Travel Club that was invitation only for people who gave them lots of business, although the terms were not disclosed. I had it, loved it, and flew about 3mm miles on SR in the next few years.

Then I moved to the US in April 1981 and my new colleagues, all of whom flew constantly, began talking about the American Airlines AAdvantage program. I did not fly them so ignored it. Moments later PanAm had AirPass, TWA had a program and I then signed up for all three. Then others...

Now I have roughly 8mm miles on AAdvantage many of which transferred from TWA. The PanAm ones transferred to UA and to DL. The addiction stays.