These companies dont give loyalty points out the goodness of their heart.
They do it to keep track of us. Where we shop, how often we shop, what we buy (and what we dont buy).
They use all this info to target their deals to us and make us try to shop at their store more often. They dont care in the slightest that some points dont get used.
In fact it could be argued that if "spare" points went to charity then some people may deliberately NOT use their loyalty card, in the hope their points go to charity.
And that would defeat the point of having them.
So not a chance of that being introduced.