
actually the reason behind that has a couple of layers but basically horses have a bit of a history in art
because since the beginning of time horses were humanity's biggest animal helper they were depicted a LOT in art/drawing/painting/sculpture which is why you'll often find posable wooden horse models in art stores but not other animals such as dogs or cats this is because horses are WEIRDLY hard to draw so often times a lot of these mahnwa artists (that are SLAMMED with work and are barely keeping their sanity) will use ready made brushes (stamps) of horses OR they'll sort work out of a real life photo of a horse hence the noticeably artstyle and texture
Why are horses in manhwa always a bit strange looking?