I see this question asked over and over and nobody ever responds. In fact, any question I ask that has to do with features Squarespace does not offer gets ignored. I cannot be the only one out there who wants these things or has these questions.
I have taken a LOT of time researching on the web, and there does not seem to be a real simple and inexpensive solution to this. You need a loyalty program third party, then in some cases, you need another third party to connect Squarespace to the loyalty software... UGH... It seems completely crazy nuts and either too complicated or too expensive for me.