There's absolutely a sexuality aspect to it, but that's kind of the point I'm trying to express here. Let me try to focus my autism on the subject for a moment, and try to better articulate the thoughts in my first post.
The sexual factor of the sheath is something I associate with the sexual dimorphism of ponies. It's a plainly visible sign of "male", so to speak, in the same way that a mans well-toned muscles, facial structure, etc can immediately read as "male", which can also carry an innate sexuality.
Now, the absence of something as simple as the sheath might not normally be a big deal, but in the context of equines, and by extension MLP ponies, it's actually a very big deal when you think about it.
When it comes to equines, there's actually very little sexual dimorphism. Unless you know specifically what to look for, it can be very difficult to differentiate between a mare and a stallion/gelding.
That's been the fandoms big meme for years. /mlp/ is constantly posting and replying to pics of real life stallions and geldings, genuinely thinking that they're mares.
Meanwhile, the one feature that can make it easy for anyone to differentiate between a male and female at a glance, is the sheath.
Or a butt view with a flick of the tail
Of course, to get around this issue FiM ponies have had a degree of sexual dimorphism added to their design. Mainly square muzzle vs rounded muzzles, human voices, and to a lesser degree body shape and size.
Even so, the conclusion I'm trying to express here is that while it's a small detail, the sheath is a critical component of the masculinity and image of male equines/ponies. The absence of it, while understandable from a show perspective, brings with it a degree of feminization.
Hopefully this makes more sense.
>can't name an artist that draws sheathes and isn't either a porn artist or penis aficionado
Aren't we forgetting someone? /bug/'s very own? >>4352
wonder if we'll ever get to see another draw from him with improved drawing skill that includes a sheath