Part of the problem with littering in mines, is unfortunately, a knock on effect from the actions of the miners themselves.
There are many underground places where litter has been left for may years by the people who worked there.
One of the worst examples of this is in one particular chamber I can think of in N Wales, where a thousand black bags would be needed to make a dent in the rubbish pile. A rubbish pile that was created by, and left by the miners themselves.
It follows then that if the modern day explorer does not possess an intrinsic respect for the environments they operate in, then they will just see their actions as 'more of the same'.
The problem of course, is that to reach them and make a difference, their morals and values have to be challenged at a fundamental level. This is an almost impossible battle, so unfortunately it is always going to be down to the same people to try and set an example in the hope that others will follow.
While we are talking about littering mines, equally reprehensible as far as I am concerned, is the practice of spray painting arrows over every available surface by those explorers who cannot seem to find their way around fairly simplistic systems without them. They are at least as visually repulsive as seeing sweetie wrappers and beer cans on the floor, and for me, seriously detract from the whole 'exploration' experience.
If it's raining, put a mountain on your head