Self-scan in Mr Sainsbury's House Of Toothy Comestibles remains a no-no for this Unit as it requires a Nectar card. And I haven't used mine since they decided to get into bed with the Daily Heil.
tl;dr if you pay with credit/debit cards then you're still giving them the same information that can be linked to you in just the same way. They don't need a nectar card to do this, they just need one (or more) constants such as payment cards. If you've ever used those cards (or previous versions of those cards) with a nectar card then they've already linked them to that other information.
Longer version:-
I got a half price Garmin thanks to my Nectar card (in a roundabout way). I also get ~£100 a year for using my Nectar card.
A few years ago our work health insurance was through Vitality. This meant I'd get 'Vitality points' for doing healthy things (and giving some information to the company obviously, but then they had some sort of access to my medical records anyway). I linked my Garmin Connect account so it would give me points for cycling (commuting), running, etc. I got points for linking my Parkrun account and for each parkrun I ran. But the most points I got was from buying fresh fruit from Sainsbury's (which it got via my Nectar card which I linked) - I didn't eat the fruit, it was mostly for my wife/daughter, but Vitality don't know that. They just thought I ate more healthily than I do just through my shopping habits.
This was enough to push me up to the top tier of Vitality points which gave me 50% off a Garmin. I bought a brand new one and sold my existing one for essentially a free upgrade.
If I'm using Sainsbury's anyway (it's my closest supermarket and handily there is one between home and daughter's primary school) then I'd rather take the free money (it's about £100 a year through Nectar points for me) and give them a little bit of my personal information and buying habits (albeit confused by buying for 2 other people in the house).
Without a Nectar card I'd still buy things in Sainsbury's, and still give them pretty much the same data but instead of being linked by a Nectar card it's linked by a limited set of payment cards (who uses cash?!?) and not get the £100 a year in kickbacks.
I've fallen out of the habit of using the reloadable gift cards which we could buy through work for a 5% discount. That means a £300 shop (which I'm doing every 2 weeks or so) would give me £15 back. I really should as that's close to £400 a year for just a bit of faff remembering to top the cards up each time.
(*Checks*, they now do "instant vouchers" for Sainsbury's which can be bought at a 5% discount and used to part or full pay a bill. All through rewardgateway.co.uk which I think many different companies use for their rewards system. I can still buy the vouchers with credit cards too, so I keep on getting air miles.)
The first world problem is obviously that it's a bit of a faff to remember to do vouchers/etc ahead of time in order to save close to £400 a year.
