Why the Nicknames?

Why is it that in every romantasy the MMC has to have some sort of cutesy pet name he calls the FMC? And why are they always the most cringe inducing things one can possibly imagine?

I initially loved the nickname "Violence" in Fourth Wing... but then she wasn't violent at all. It really bummed me out, because it would have been a great nickname but it was totally un-earned.

Anyone else hate romantasy nicknames? What are some of the worst you've read?