Waitrose only allows you to apply two vouchers per shop, although I suppose you can split your shop up and pay twice? Seems like a faff, and I bet most people won't do that.
I haven't been to Sainsbury's in ages and I didn't have time to do it this time, but I always used to go back after a break and buy one item and then get given a bunch of vouchers - often a double or triple nectar points one - that I could then use for my actual shop there and then, rather than spend a load and get a voucher to use within a week that they are banking on you not using (because you just did a big shop!).
After paying, I got no vouchers. Have they stopped issuing them from the tills now? I don't get any notification from the app of vouchers, and haven't really got time to go searching for emails. I think it means it will be a while again before I shop at Sainsbury's.
Meanwhile, my local Tesco is not budging on turning off the hand scanners at 2100 despite advertising them as being usable until store closing time. They won't change the signs because company policy is they are to work when the store is open, but the staff are still told to turn them off. When I brought this up on a Tesco staff forum, I discovered that around 50-60% of stores turn them off early, to save on having to return them and have staff on standby to do random rescans etc.
Yet they still won't change the signs! I assume someone high up at Tesco wants them operating but is willing to turn a blind eye to the practice. Very odd, and annoying as I like doing big shops when stores are quiet and I'd rather go at night than first thing in the morning (and I don't know if they don't do similar then by not activating them until later in the day after opening).