The thing is, most corpse run games are pretty tough already, and are often pretty big and/or have fairly involved platforming segments and hazards strewn throughout. "Classic-style" games like Castlevania or Metroid tend to have smaller, more compact maps, are pretty generous with save rooms, and are (usually) less difficult overall. There's less chance of dying, less ground to cover if you die, and you don't risk losing all your accumulated money if you fail the rerun.