My personal point of view:
They gain much more attention in Japan because they are considered as rookie in Japan music industry
Thus, it is quite impressive for new artist to gain more attention.
However, for korean music industry, KARA has small fanbase considering being in the industry for several years.
(I saw the figure about their fan, some artists who debut after KARA have more fanbase!!)
That's why it is quite hard to win some awards that mainly base on the vote.
(Btw, I think MAMA award is totally biased....they are other artists deserve that award in some category)
Nevertheless, I believe the sales in Korea is impressive enough...regardless of whether they receive award or not, the sales still prove that they are popular and loved by their fan like us