There’s no “justification.” It’s laziness first and foremost. It is sometimes influenced by logistics, such as no trash recepticals being available. But that’s still zero excuse, really.
The only time littering might be in any way shape or form understandable, it’d actually probably be called illegal dumping. If you’re so poor you can’t afford trash removal, you might end up resorting to illegal dumping. But again, much different than petty littering.