Honestly I think it comes from your exposure to "art" and what you "studied". People who came from traditional art are taught that there's no "lines" to anything; it's all different shadows creating the shape in space.
People who come from trying to draw kids shows they liked as they grew up and not taking any formal art classes after, or during, likely are more into lined art.
I'm a mixed bag of both. My coloring style follows the "traditional art" aspect of light and shadows bouncing around, whereas I want my lines to be present. People who can do super skimpy lines amaze me - I can't work with lines that thin unless I have a hack (Paint Tool Sai's linework vector tool lets you make lines thinner once finished, if you started in it first, but the overall line's appearance is a hard ink, not soft... sooooo).
For something to look at and admire, anything that's lineless or has hidden lines (lines that blend with the colors but are present and can be seen) are really fascinating to me. These are both techniques people who do traditional art I've seen - copics, watercolors, guache, ect. Most digital artists I've seen tend to use harsher inked lines, or more contrasted shadows. The book series from Japan SS+ I think it's called, has fan-submitted work with a few tutorials every 3months or so, and it's really fun thumbing through everyone's art.
