So, here's a new idea, or maybe a meta-idea, a setting that can justify all kind of snuff show stories where snuff isn't as common as to need extreme numbers of population or extended life span, but still there are willing victims who do it for the viewer's entertainment.

The idea is that public executions used to be a popular entertainment. But eventually as the society progressed they started viewing executing prisoners as inhumane. However while the more enlightened categories of population insisted on banning capital punishment, the general public still wanted their bread and circuses. Bread aside (or maybe there can also be a cannibalistic aspect to this too if you're into it), the compromise was reached that as long as the victim is willing it can't be considered inhumane. The first willing victims could possibly be the humanists themselves, setting an example of how inhumane executions of unwilling prisoners aren't necessary anymore and can be substituted by humane executions of willing volunteers, to show how such shows can be no less and maybe even more entertaining (so they might by themselves come up with more entertaining ways to be snuffed to emphasize that idea). People indeed find it entertaining and become more acceptable of humanist ideas which in turn leads to more willing victims. Eventually the executions lose their negative connotation as associated with punishment and become just a form of entertainment. At which point performing on the gallows is seen as mostly the same as performing on the stage. Which makes volunteers even more willing, after all what little girl doesn't dream of being a star? When the whole thing started pre modern times entertainment might not have been the most respectable profession, but nowadays they're the stars, whether they're actors, singers or snuffets.

As for a more specific story set in this setting, an idea comes to mind where a young J-pop idol, or maybe an entire band, tried their best in their idol career with the sole purpose of gaining popularity and thus most possible viewers for their eventual main event: execution.