I've heard that many deaths ruled suicide might be better classified as signaling botches. That is, the individual in question was doing something with the lowest available probability of actually killing them, which would still be recognized as a suicide attempt and thereby provoke reassurances. A multifetish scenario would be far enough outside societal norms to be unlikely to attract support, and virtually impossible to survive.

In other cases, it's a matter of extreme altruism, not wanting to be a burden on others. That's more compatible with the psychopath/necrophile/cannibal option, but, statistically speaking, so few people empathize with any of those demographics (let alone all three) that they aren't common targets for even minor altruism, let alone literal self-sacrifice.