I'm a fan (and you should be too) because...
a) their music makes me feel like my life is beautiful
b)every member of the band has something to offer, they all have their own style and meaning, they perfect each other
c)the videos are inspiring
d)the art is amazing
e)the fans are intelligent and this place has a good vibe
g)they can perform
f)they are funny

etc...

In conclusion... why on earth shouldn´t I be a fan? They are Incredible.