It's only SE IFR or night charter that's banned, and yes its the survival aspects of having an engine failure at night or IMC that is the issue. SE Day VMC Charter is still allowable as far as I know, been a while since I've done one, so have not looked at the rules recently (pretty sure a lot of activity up north fits under that category).
I do remember AD-ENG-4, put an end to a lot of casually used SE charter aircraft. The additional requirement that charter aircraft had to have all components within time limits or a specific maintenance program made most our ad hoc charter planes drop back to airwork category to remain "on condition".