In general, store points and so forth are something that stores hope you'll perceive as being of greater value (and hence encourage loyalty) than they'll every have to actually deliver on.
The norm with grocery stores though seems to be more in the vein of giving instant savings to card holders. Some chains (Safeway out West is one of them I think) have so many and such deep special prices that I have a card even though I only shop there on vacation sometimes.
(Interestingly, Shaws--which is an Eastern US chain now owned by European company I believe--discontinued their card in this vein a few years back.)