1. There's a lot of members in one group generally. Of course there's gonna be one of your taste among all the members. Therefore, it's also easier to gather fans of all the group and fans of individual members. Also, because they have a lot of members, they can send each member in different directions like acting, musicals, radio DJ, etc. and keep the group alive like this. For the groups that doesn't contain a lot of members, each member will have a lot of individuality
2. They have killer visuals. There's a lot of people who label SM as the Sooman flower garden, compared to your average other groups, the overall visual is all higher. (Even though they have ugly members, with SM's care management, they can turn them into someone decent. SM's costumes and makeup styling are all high quality.)
3. Their skills are all above average, each member's skills kinda makes up for the 1/3 of the entire group's skills. That's why there's a harmony created in the group. Taeyeon, Tiffany, D.O, Baekhyun, Chen, Luna, Kyuhyun, Jonghyun, etc. all have outstanding skills so they're gonna be more apparent. Seriously there's not a post that talks about good idol singers that doesn't mention SM
4. Each group is good at variety shows. I'm not an SM fan, but I even find myself watching SNSD and SUJU's broadcasts. Even for EXO, their Showtime show was rather fun and there's a lot of funny members despite their situation back then. Ryeowook and Jonghyun are even in charge of their own TV show. Even Sunny is trying out as a radio DJ now.
5. There are people saying that SM can't rap, but ever since they made NCT, they're moving more towards the hip hop scene so I think they've opened their opportunity to show off their rappers now. When I listened to NCT, compared to the normal rapping hook, they're above average.
6. They're recruiting foreigners in the team so it opens the door to promote overseas. Of course it happened that some members quit to return in their country, but it didn't really shake the popularity of the group.
7. Their songs are hit or miss, but for people who enjoy SM's songs, they REALLY enjoy the songs. There are a lot of addictive songs with catchy hooks. Actually, the songs who are the most acknowledged by the general public are SM songs, if you walk to the street, anywhere you go, there will be a least one SM song playing. Fx has a lot of songs that misses at first but becomes more and more addictive as you listen to it, EXO's Wolf and Growl are also very addictive. +Nowadays, they've been into EDM and since it's the trend, people listen to their songs a lot
8. SM has a throughout copyright system applied on their singers. Everyone who uses their works will have to pay for copyrights and it's a huge amount.
9. SM includes a lot of morals/life values/things to reflect on in their works. If you don't know SM, you might not know, but groups like EXO, NCT and Shinee all have MV analysis that will induce goosebumps. Even for girl groups, their MV are high quality and the story is very substantial.
10. Their B-side tracks are no joke. There's ballad and other addictive songs, I like that SM puts whatever they want in the album. There was EXO's seasonal album December and recently SNSD released their Fan song, when you listen to SM's ballad, you'd know that SM really choose their songs well.
11. Even though there's a lot of groups in SM, they plan the promotion rotations very well. There's also a lot of comebacks. That's why you hear that the end of the year will be an SM party.
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