As far as walking on the tracks, there are a number of places on numerous Swiss scenic trains, especially around the Engadin, where after both trains have crossed and left, the best (only) way to cross from one side to the other is across the tracks.
Just because you can't see (or don't look) what you are walking on and in doesn't mean it isn't there.
It is particularly unpleasant (and unhealthy) for workers working on the track or maintaining it. They get sprayed as the train passes, and when they have to maintain the track it is like working in a sewer. And track workers don't get full body suits.
Trains with no holding tanks are not nice anywhere; and that is the case with many older trains throughout Europe.
I am active in the campaign to either retrofit tanks or replace trains in the UK.