Why is litter a recurring problem in this country?

So when I have the time, I do some pretty intense litter picks and actually it goes beyond picking litter and also collecting fly-tipped rubbish (of course, not the fridges, sofas or mattresses though ;-)). Something I’ve wondered though is first of all - why do people do this? I come across areas in my town where it just seems someone finds a nice hill/slope and decides to tip the contents of a huge rubbish bag down that hill, creating a huge mess that’s also a bit tricky to remove fully. Something I’ve also noticed is when I’ve cleaned it up, oftentimes (though not always), the place goes back to looking like shite just a month later. Someone new comes along and dumps another bag’s worth of rubbish down the hill, creating another enormous mess. Why? It just doesn’t make sense. Even if people have got issues disposing of household waste, what could possess these people to just scatter all that rubbish around an extended space? Boggles my mind. I like making efforts to clean up the environment, but sometimes it actually gets difficult to do it especially when the same thing keeps happening over and over.