Exactly! I mean of course he had no reason to even think of getting married that was until one Chloe Decker came into his life 😉
Also Hell? Not a great way for a proposal. Too hot I don’t think Chloe would survive the heat or coldness - she either die from overheat or hypothermia.
Heaven - would be perfect if 1. Lucifer wasn’t banned and 2. Chloe is not dead so she has no reason to go up there
So that leaves earth; on the beach where the shared their first kiss. Ooh! A beach-themed wedding- probably not ideal for poor Lucifer 😆