First create the problem, then create the solution
Sales receipts from retail stores used to be a simple thing. Back when they didn't integrate their cash registers with the payment devices, sometimes you'd get two of them: one for the items and another for your credit card. They eventually got this figured out and onto one receipt, but something else changed. They realized they could use receipts for more than just information about what you bought.
More and more places seem to be getting into this. It seems like you can't escape from a store these days without receiving three feet of thermal paper. Maybe the top 6 or 7 inches is directly related to what you actually bought. The rest is monochrome logos, surveys, slogans, and yes, advertisements for other products.
I suspect some of these places will eventually figure out the next evolution in this process, which is to offer to just e-mail you a receipt. You'll have to sign up with them somehow, of course. If they already have you using a store-brand "club card" (aka physical cookie), then it'll go there. Otherwise, perhaps the businesses will link up with one of these multi-retailer "loyalty card" schemes to push receipts through their systems.
Once that happens, there will be a good reason for people to bother with those cards even if there are no discounts to be had. Just the reduction in paperwork alone will probably be worth it for many shoppers. This means the stores will have yet another way to tie all of your real-world purchases together, with all of the marketing signals that entails.
It gets more interesting, though. The mails they send you will probably also have all of the logos, graphics, slogans, and fancy advertising just like the printed ones have right now. The difference is that any links from those mails will have some magic tag in them. The first server which handles that request will notice your unique ID and will set some kind of tracking cookie. It'll just so happen to be served from a domain which is used in a great many other places. When you go shopping online, your browser will cough up that cookie every time it gets a resource from that tracking domain.
This will then give them the ability to associate your online browsing with what's happening in the real world. Previously you'd have to actually buy something online for this to work, but now they can "tag" you just by having you follow a link from a "bricks and mortar" sales receipt.
It's brilliant, really. First they create the problem of ridiculous receipts that nobody wants to be stuck carrying around, then they create the solution of letting you divert them to e-mail. They'll sell it as a way they're doing something nice for you by eliminating those huge receipts from your pocket or purse. This will probably work, too, assuming people forget that the stores are what made things so huge in the first place.
Given enough time between steps, you can get away with a lot of things.