There is a point of affection you reach when terms of endearment like “honey” or “sweetie” seem the most vulgar, paltry things. What could be more endearing than the actual name itself? I can’t imagine anything other than those syllables, even when uttered inside your own head in a quiet room, being more potent or evocative.
At some point I decided that I would rather take two real names, spoken to each other in equality (just as between two friends), over some weird cultural convention that makes us feel like we have to develop “pet” names for each other. I feel like the practice is more often something that we do because we think that it’s something that people in relationships do. Our relationship with someone gets to a certain point and we try on using “baby” like an awkwardly fitting sweater. After all, wouldn’t others doubt our affection if we didn’t say those things? We tend to shove pre-frontal cortex decisions onto some things that should be limbic.
So cynical it seems, I know. …But I’m not a cynical person! I think that somewhere, some very old couple who have managed to love each other’s company for 50 or so odd years have probably figured out an unhypocritical way to use pet names. But they aren’t “love” or “mon petit chou”, I’d wager… Probably something more like “old spongey.”
Edit: It occurs to me that Ursula Le Guin has an interesting take on this in her Earthsea Trilogy. The characters in these books have a common appellation that they go by in public, while their true name is kept private, only revealed under circumstances of great trust. Rather than using pet names among intimates, people who are close use true names. I like the idea of the close/privileged name being the one that is more real, I suppose.