Not My Bag!

Sorry but I am just going to have a wee rant!
A couple of days ago, Mag & I did a "womble" round the wood and filled two black binbags with rubbish: mostly plastic bottles and drinks cans but there were quite a few filled doggy-poo bags which had been used, tied off and lobbed into the undergrowth! As the plastic degrades very slowly, potentially these bags could hang around for years and years!
I simply cannot understand the mentality of whoever is doing this. It says quite clearly on the bags to "bag it and bin it" so what's the deal?? How easy can that be??I know all you dog-owning blippers are perfectly responsible but somewhere out there is a muppet who seems not to understand a very simple instruction.
Rant over, normal service will be resumed as soon as possible.