"I'm so not sucked in by corporate manipulation...
But, if I can find a way to save some dosh, I will."

And the way you and many people have found is exactly the way a corporation wanted you to find - odd that. Rather than going to the effort of shopping around to force price competition amongst retailers, people prefer the convenience of feeling they're saving money via a retailer's baroque "loyalty" programme.

It's a classic "spend to save" scheme. In order to collect your "savings" points you keep going back to one retailer, and buying their offerings without seeing if the items are cheaper or better elsewhere. The more stuff you buy, the more lovely, scrumptious reward you accumulate. Overall you end up paying more - that's why they run the scheme. Plus they get to monitor and profile you as a consumer, enabling further manipulation.

"I left my card at home once, so I actually drove out of the filling-station without filling her up, just so I could claim my Nectar next time."

It's a very effective scheme, to be sure.