>>42725975
Twilight definitely has the most art in the series.
as for why, I think it's just something that fits her character.
She's a dignified lady, and so that's how people like to portray her. They like to show her elegance and sophistication in poses that you might see on classical paintings.
Fluttershy in more natural poses could be because she's generally more in-tune with nature. Being shy, she wouldn't really understand her own sexuality to pose sexily for a photo.
Sunset and Twilight's focus on their butts could be for different reasons. Maybe it's just what people want to see, or it's just more alluring to imagine the nerdy bookworm, or the edgy bad girl offering themselves to you, the viewer. Those two in particular are pretty easily made into everyman blank slates because of their main character status. It's a lot easier for someone to just decide on them when they just want to use a character from MLP or EQG.
As for why Dash is usually in pony form. My best guess is memes. I like quadrupeds as much as the next brony, but even I expected it to be a lot more niche. in general. She's pretty much the poster child of the show, even being confused for the main character by some people just getting into it. So maybe it's a combination of people just liking her pony form, being the center point of memes, and generally where all the die-hard horsefuckers gravitate around wanting to cum inside.
