I imagine that the cost of a weekend camping ticket made the cost of a tent a minor consideration.
The organisers could easily resolve this problem by insisting that camping ticket purchasers have to buy a disposable tent with the ticket - produce the ticket on arrival, and pick up your disposable tent.
The tent i used in the '70s was a few years old at the time and still used into the '80s... we don't throw good boots away when they get muddy!
There's a great irony in the young generation that claim to be the anti single use plastic that pollutes the earth generation, and then leaves these tents which is like leaving thousands of empty pop bottles on a beach after the skinny dipping party...
The organisers pointed out that there is widespread belief that charities put the tents to a good use, and that the practice of abandoning their tents for a greater cause is a red herring. The reality is liat they just get skiped in the race to clear the site within 24 hours before the hand back of the land.