Blowjob scenes are the backbone of hentai, and if you've browsed even casually, you've noticed how many episodes and doujinshi treat them as the main event rather than a warm-up. There are practical reasons for that, and once you see them, the whole genre makes more sense.
Why there's so much of it
Oral scenes are cheap to animate well. You need two characters, one fixed camera position, and a lot of close-up frames. Compare that to a chase scene or a fight, where every second means new backgrounds and new body positions. Hentai production budgets are a fraction of what regular TV anime gets, so studios lean on scenarios that stay in one place. A single well-animated blowjob scene can eat half an episode's runtime and nobody complains, because that's what the audience came for.
This is also why the scenes get so much creative attention. When the entire budget concentrates on one act, you get exaggerated expressions, drawn-out pacing, and detail you won't find anywhere else in the medium. The craft is real, even when the anatomy is not.
Censored vs. uncensored
Japanese law requires mosaic censorship on genitalia for anything produced and sold in Japan. That means most raw hentai ships pixelated. Uncensored versions exist because publishers license works for overseas release and publish them without the mosaic — FAKKU is the biggest name doing this, and they've been at it since the mid-2010s with official licensing deals, not leaks.
Here's my honest take: the mosaic matters. Some people tune it out, but I'd rather pay a few dollars for an official uncensored release than watch a free censored clip at half the visual quality. It changes the scene from obscured to,