It is like asking why do people like sonic characters (sexually) people liking anime characters, disney characters etc. beyond your imagination. So your question is not hard to figure out, or anything. It's just a simple answer; because they think she's hot. There that simple.
Here is why
1) People think she is just hot, but i would rather say she is beautiful
2) She is very powerful monster and she might have been very popular because she is the student of Dark Magician
3) she has a good ability
4) She is actually a good friend of Atem in ancient times