Sometimes couples find it attractive, others just use it because it’s more comfortable and a cultural custom.
Precisely because Hyung or Noona means big brother and sister is that when you use it between a homosexual couple it is closer than address the other as Mr or Ms. It's more familiar, more intimate, not necessarily like siblings but more like family. When you see heterosexual couples you usually see them use -ah the same way moms use it on their children. More than respect, is closeness and familiarity depending on how comfortable they are. -ssi is usually meant towards someone you feel great respect for and is better than using ahjussi (old man) but still draws a line and doesn't signify you're close with the person. In Asia honorifics not only highlight the age gaps and power dynamics but it also says a lot about the relationship people have with each other and how deep their bond is or overall familiarity. I'm not asian myself but I speak i ntermediate mandarin and see these dynamics among my friend's family and friends and also in other languages i consume the media of. Hope that helps.
Yeah hyung is more intimate than just names, iirc it's used between like friends of the same age or brothers, or relationships. Like how oppa can be used from a woman to an older brother, older platonic male friend, or boyfriend, whether it's romantic or not depends on the context. But it just can be used to signify closeness with that person
Could someone please help me understand, why in manhwas do couples use honorifics, like I understand it's part of the culture and you use it everywhere and I respect it, but I guess I just never understood why they use it as a couple, like yes you use hyung bc you respect your partner but wouldn't it feel more intimate and personal if you use each other's names? Like if it were me I wouldn't feel as close to the other person if they called me older sister or something, tho i can't really talk on this since I'm not Korean, does it feel normal for you Koreans? And can someone please explain how hyung would be an upgrade from Hyeonseon-ssi? Please and thank you :))