Not just in manhwas tbh, strap-on usage is rare in GLs, period. Personally I'm not too interested in straps in smut but it's annoying how rare it is to find a story that features it, like I can count only maybe 3 off the top of my head that has them.
Idk why but in gl manhwas they rarely ever use strap ons unless its like bdsm involved.. Like whats up with that?