JE boys...xD They're heavily promoted because many of them are not only singers, but also actors and appear in many magazines, photobooks, etc.

Like Eclipse said, their has been a decline in physical sales within the past few years. Since you can download your songs from iTunes and such. And many artists' work tend to leak much early before the release and you can find them easily. A popular artist like Hikki, it's very easy to obtain a download for an full album. Even though they're meant for 'sampling purposes'...do we really delete them after 48 hours? xD