I have admittedly not done much thought in regards to destiny. The information I have has always been that players don't need to choose destinies for their heroes at the start of the campaign. Not every hero has a Destiny that must be fulfilled before the end of the campaign, and even players who want their characters to have Destinies need to give their characters, and the campaign, a chance to develop first. That said, I'm not particularly against incorporating them yet.
If people want to predetermine a sample destiny they'd like to utilize just in case, that's cool, I'm just saying I don't have plans for it yet.
Were I to choose backgrounds over destiny, which I might as it reflects the tone much better, I'd probably inform everyone to add that snippet to their sheet. As it currently stands, I feel like we're using a lossless, theater-of-the-mind approach for this RP. Somewhere between the mechanics of the TTRPG and the freeform play-by-post narrative we're accustomed to. As such I asked people to write up their character's synopsis, which to me is like making a background but without the meager choices of event and occupation backgrounds.