A gallery of completely shaved idols prominently displaying their lack of pubic hair in what in Japanese is colloquially termed “paipan,” a term thought to be derived from the shiny tiles of mahjong.
The fetish for completely or heavily shaved genitals which has overtaken the western pornography industry and subsequently entered mainstream fashion has had minimal impact on the Japanese market, and “paipan” remains a small fetish market (although in 2D erotica the difficulty of drawing convincing pubic hair doubtless accounts for the frequent lack of pubic hair seen there), with correspondingly low sales and an accompanying inability to attract the sort of relatively attractive AV idols seen in mainstream works.
Regarding the actual reasons for a lack of enthusiasm for heavy shaving amongst Japanese females, Wikipedia suggests this is due to the practice of genital shaving being common amongst harlots of the Edo period red-light districts, causing a sense of opprobrium about the practice (although just why western women take so readily to a practice popularised by Californian pornography and extremely revealing swimwear is an interesting question).
Since Japan has a well developed culture of public bathing, women appearing at onsen or public bathhouses heavily shaved, and amidst gossiping neighbours and bemused children, may thus experience some discomfort and attract unwelcome attention, discouraging them from a practice chiefly associated with prostitutes and fetishism.
Where pornography is concerned it also looks likely shaved performers rule themselves out of appearances in mainstream material until they regrow, perhaps explaining the lack of available strumpets to appear in such productions.
This does not mean there is a complete lack of appealing material however: