Can someone please tell me why these charities put bags through our letter boxes for us to fill and then not collect them?

In the last few weeks I’ve had four (two Children Air Ambulance, Breast Cancer, Fire Fighters and Make-A-Wish). 

I’ve put the bags out at 7am and they were still there at 9pm.

I will not be putting any more out in future.

J COOK
Headington