Different flights and tickets give you a different number of miles. If you are serious about accumulating miles you can spend a great deal of time and effort attempting to optimising how many miles you earn.

If you just 'attach a unique identifier to your account' you aren't going to get much out of a frequent flyer programme.

>If you just 'attach a unique identifier to your account' you aren't going to get much out of a frequent flyer programme.

If you're on a consistent route (ex: SF to NYC or London) picking an airline and sticking with it when you fly in every week/month will absolutely rack up points.

Acquiring points is simple. Redeeming them requires a non-trivial amount of work.

Personally, I wouldn't even call acquiring points simple. Right now when I fly it's complicated enough to pick a flight. But one of the points of a frequent flyer program from an airline's perspective is to encourage me to fly their airline more often. So if I belonged to one of the programs, I'd also have to be doing the calculation of, "Oh, if I fly X instead of Y, I'd get enough miles to level up in status and/or get a free goodie." Which means having to learn and keep up with the rules, balances, and rewards of the various programs.

Do not want.