@basedbagel I think the reason is they are overly attached with emotional dependency.
They are crazy for you. So you do not need to worry that they will cheat. When they want only you.
I think anime give her bad reputation. Because they often are too crazy like psychopath or sociopath.
Another problem is they often are portrayed as crazy girlfriends.
Who would not want girlfriend that would be crazy for you.
@basedbagel To Each Their Own.
We are all differnet so choose what will work for you.
This is why there is many dere types like tsundere, yandere, kuudere, deredere and dandere.