
(sorry for any mistakes, my English isn't that good).
This situation depends a lot on the person, and it's easier to use 3D models a reference than looking for people to model for your drawing or having to buy small articulated mannequins.(many sites ou apps 3d models are free)
Traditional artists use references mainly those with a realistic style. It's not always easy to draw without some type of visualization to start. Furthermore, in the manga/manhwa industry where you have an extreme deadline you have to look for things to speed up the work, and it's a sad situation after all art take time to make it good, but not everyone has that time or the money to be dedicated and do a incredible job.
(Sorry if anything that I'm said sounds rude, that was not my intention, I'm just like to have conversation and show my point of view)

Ok, looking at some of the painel, you will se that some of the lines on the drawing look diferentes, for example in one part of the drawing, the clothes have some lines that are thick and stiff them other parts were the lines are more thin and smooth. And sometimes it's the shade, you look and says "that's 3D" but this topic is hard to explain
I don't now if you ever have see 3D models for artist to use, but normally when used they have that aspect of stiff and thick lines, since you read manhwas you probably have seen the famous teacup, she is a 3d model that is used for various manhwa artists
First I noticed the obvious 3D in the hands, which is normal after all most artists have problems with their hands. But because I realized this, my brain started to perceive the 3D of the other parts of the drawing, it gives me ick, because it doesn't look harmonious, you can clearly see what is 3D and what was actually a drawing.
Why authors why, you did that, could just used the 3d models has references, if you gonna trace the model alest make look like is the same style.
Not judging the author for using 3d models, wen I'm being lazy and drawing something to myself I'm do it too, but to that to a product for me don't make sense