In one sense, certainly not, for example I have 2931 points, in theory that's £14.65 value.

As this story explains, if you knew the 11 digit account code for those 2931 points you can just rock up to a Sainsburys store with the appropriate code on like a piece of paper, scan it with the reader, and it'll conclude you're me (that's my code after all, that's what I do when I shop with them although my code is printed on a little plastic card they gave me) and therefore you can "spend" my points, typically in lump sums of £5, so you could buy £12 of booze, take 2x £5 = £10 off the price and spend £2 on booze that costs £12.

You can't turn it directly into cash, but obviously goods like booze, electronics, jewellery which are all potentially available are very easy to turn back into cash at a discount.

No, you can cash them in to get money off products. You can also get cheaper prices. But some people spend months saving up.

You can bet your bottom dollar that if you found a way to add points, they would lose their minds.

Each point is next to worthless, but if you shop at Sainsburys regularly you can build up quite a balance which can be used for very real money off.

There was a court case some years ago about an IT insider at Nectar assigning themselves points fraudulently and then spending them. He received a pretty hefty prison sentence: https://www.bbc.co.uk/news/uk-england-london-12189919