Unfortunately there's a cost involved in 'scrapping' a tyre these days (although I believe many are recycled in some way) Even the tyre places that take the scrap tyres from you are charged for returning them, so if they don't charge you directly for it, you can be sure it's hidden in the price of the new tyre/fitting.
The idea of finding another local authority that will take them from free is a good idea, some are now asking for ID to confirm you're from the local area.
At the end of the day, yes it's an extra cost, but it's not that big an amount. Would it be highlighted as much of an issue if the cost of a new tyre increased by £5? It's just another running cost - an extra £10 every so often. I'll still be doing home changes as It's still cheaper than paying someone to fit them for me.