So basically, the answer is because they're ugly. People can't stand to look at them. I guess that's your opinion, I don't think she's that ugly.
Pretty much all about personal preference when it comes down to villagers in any Animal Crossing game. Some people want certain ones because they're so popular, others want ones that are undesirable. Many people I've seen want villagers they had them in previous games. Some just don't care what they look like and keep them around until they get their pic or ping to move.