The east and the west have fundamental philosophical differences, and it is the same with idols. Japanese idols are Western idols different. This page explains the difference very well.

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In the West, "idol" usually refers to young and glamorous pop stars, ~ they're produced to appear as perfect and glamorous as possible.

But Japan's idol culture is different. Part of the allure for idols is a girl/boy next store attainability that Western idols lack. In most cases, they are not supposed to seem larger-than-life; in fact, they're supposed to seem approachable, like someone you might already know in your daily life.

For Westerners idols are the characters they want to become or the characters they want to have as a partner. The embodiment of their ideal personality so their idols have to be bigger than life and close to be perfect, but Japanese people don't expect idols to be bigger than life or perfect. It's quite okay for Japanese fans if their idols are talentless. What Japanese fans expect idols are accessible image, a feeling of closeness, a feeling of family member or close friend. For Japanese fans, idols of opposite sex are virtual lovers, and that is why dating ban exists in the Japanese idol industry. Minami Minegishi (pictured 2009) made international news in 2013 after a video of her with a shaved head as penance went viral.  For the Japanese boy fans, a girl idol dating a man is betrayal and adultery against the virtual relationship between them.

Then the next question is "Where does the difference come from?". Kunio Yanagita, a Japanese author, scholar, and folklorist, once pointed out the difference between Western education and Japanese education. He said Western education is to make a child someone special and superior to others, but Japanese education is to make a child an average person. This explains the difference between Western idols and Japanese idols. The ideal character for Westerners is someone who is superior than others. The ideal character for Japanese or other Asians are someone who is ordinary.