I have always wondered?

I am hoping one of the many dog lovers in the CC can solve one of lifes mysteries~

When I am walking in the local woods ( collecting litter) I find many plastic bags of dog poo either decorating trees or often left at the side of the footpaths, frequently only yards from a council supplied doggy bin. 

What I fail to understand is why bother to pick it up in the first place as this is a wild wood not a park. It would be far better to kick it into the undergrowth where it will soon disappear, instead it is placed in a sealed bag where it can never rot down.

I am not suggesting that this is carried out by CC card carrying members but it is  becoming very widespread.

Your thoughts are welcomed.