I have a question regarding Johnny artists

[A-TeensFan]

Hey, i've been quite into Johnny acts lately (News, Kat-Tun, Tegomass...) and i've been collecting their albums and stuffs on cd japan, amazon and yesasia. i noticed that none of the JE artists have their album covers displayed on those sites, just a picture with their names. Even with magazines covers they also have to delete the singers faces. Is there a prohibition on using JE artists picture or something? Can someone explain to me? Thanks so much in advance.