Why are JAV videos predominantly low resolution?

[legshowfan]

Apart from the high degree of censorship in Japanese JAV videos, does anyone know why even the newest ones continue to be predominantly low resolution? I see very few 720p or 1080p vids.

There is a fair amount of information out there about the censorship piece, but not the low vs. high resolution. Anyone have any idea on this?

Cheers.