Hi Gaoler,
Mainly for the same reason as described above really.
If everyone has a single activation to receive all offers from a retailer in the future, while that may sound convenient, it creates the problem of users not knowing the offer they’re redeeming before they trigger them with a purchase.
By activating each offer before redeeming them, not only do we see who’s purposely activating what offer, but the user can make a more informed decision on their next purchase rather than just accidentally triggering an offer for less than its full value because they weren’t aware of it.
In this way, it benefits both the user and us.
This is my opinion on it, but it is an interesting idea and I will pass on the feedback.
I hope this answers your question.
Jack