MP, different areas have different needs, you cannot make sweeping generalisations such as "These sorts of collections ARE OF NO USE" just because you don't see any need in your particular area.
We live in a well-off area. Our church harvest festival goods DO go to a nearby homeless hostel who DO want them and say that the donations tide them over till Christmas without having to buy anything.
Our school DOES take boxes to the local sheltered housing scheme and the children DO go to deliver them, chaperoned of course. DD was one of them and was chuffed to bits to get the chance.
Whilst waiting to collect the DCs from their after-school activity today and mindful of this thread, I had a nosey at the boxes still waiting to go out. They were all full of stuff I would have been quite happy to receive - baked beans, apples, onions, pasta sauce, soup. I didn't see any Spam.
Our church also donated the harvest festival loose collection to a church harvest appeal - a charity fund doing practical work abroad. (Out of interest I have worked out that the amount given - which I happen to know - is almost the same amount as would have been raised if all the children in the infant school had given £1.88)
I would be happy to donate to Wateraid if that was suggested one harvest festival. Suggested - not compulsory. If it was compulsory I too would get arsey about it.
I would also be concerned about the organisations which, in our area at least, do depend on harvest gifts.