Well the council doesn't really offer sufficient hard waste collection anymore. I think you have to pay for it and the times they give you are probably rubbish, no pun intended.
Just checked it's £15 for 3 items. So based on that pile, that's probably £60+.
That's not very convenient for people who are short on money. And most people don't have a vehicle to deliver to the tip.
Its way easier for the council to let people fly tip (they are actively encouraging it with those prices), then let the residents put up with it, complain, then pick it up 2 weeks later once they can be bothered. That's cheaper than offering a proper service to every household.