We live in a rural area, with no shops within three to four miles, so almost all of the litter on our grass verges and in the hedgerows must be being thrown from passing cars. Why people feel the need to do that, I will never understand. It wouldn't exactly be hard for them to keep it in their car until they get home, then pop it in their bin.
On top of that, it's quite scary just how many empty wine, spirits and beer bottles appear overnight - there must be a lot of very drunken drivers on our roads.
Then there is the refuse that 'escapes' when our bins are being emptied. The collectors are presumably on a tight schedule, so don't bother picking up anything that gets dropped.
At least things have at improved a bit since our paper and plastic recycling boxes were replaced with proper wheelie bins, because the boxes used to get blown around by the wind, their lids would come off and the paper would go everywhere!