I don’t think this can actually be translated back into English… but anyways:

非死不可, to me, sounds like shortened version of 你非要死不可？(Why do you want to die so much?)

Lol I remember I used to make a lot of cross-language jokes as a kid and new immigrant…

Why do you [use] Facebook? --> Why do you 非死不可? (Why must you die? / Why must you use the website that makes you die?)

Oh I just searched Wiktionary, apparantly it’s an official entry… so it’s not just me with this joke lol

en.wiktionary.org/wiki/非死不可