Four drops for 8 people. Usually 2 of the 4 are junk that nobody wants, sometimes 3.
Law of averages says we'd need 4 runs to get one token. Sometimes it takes a lot more than that, depending on how many lalas were sacrificed to RNGesus unlucky you are with rolls. I've had weeks where it took well over 20 runs to get a drop, while others take only one or two.

It's not that difficult to implement a token system with fixed rewards. You need to do X number of runs to obtain Y tokens, that can be used to purchase the piece of gear you want.

Predictable. Reliable. Players like it that way.
There is too much variation in the amount of effort required.