you wot m8? now i'm gonna stop you right there.
ahem.
2B is far more than just popular for their looks. Yes, it's true, a lot of people no doubt like her for the sex appeal, but you can enjoy a character for more than just that. Many people who have actually played NieR agree that 2B is popular for more reasons than their looks, but it's because of the magnificent game she stars in as well. As for her personality... You have played NieR: Automata, correct? For those of you who haven't, please do not read further for I am about to drop major spoilers, but here it goes. 2B's personality isn't bland or underdeveloped in the least. She may not be the most emotional a
t first, but if you played the game long enough you'd realize why she was the way she is. She restrains her emotions for many reasons, and I don't mean because of the "emotions are prohibited" nonsense. She uses that as an excuse herself. 2B is meant to remain calm and collected most times, but only because she forces herself to. Why? Well, since I'm assuming you likely don't know, 9S and 2B have met several times before the events of NieR. They've been partners multiple times, but each and every time it ends the same way: 2B is forced to assassinate 9S at the orders of the Commander. 2B isn't her real name, it's 2E. Her job is to hunt down and kill androids that go rogue. Because 9S's curiosity and intelligence transcends that of every android, he always finds out the truth about YoRHa one way or another. Because of this, 2E is partnered with 9S under the alias of 2B, ordered to assassinate him every single time he discovers the truth. Each time hurt more than the last. In one of 9S's previous "lives", 2B freely called him Nines, she was more open and emotional with him. She ended up killing him then after things went down differently than usual, and forced herself to prohibit herself from showing emotion in an attempt to not get attached to 9S so it wouldn't hurt her as much the next time she was forced to kill him. You see this almost all throughout NieR. The times she lets her emotions/true self shine through are when things seem the worst for them. Having to kill 9S upon being infected by strangling him, when she seems to be at her end and leaves a message behind for 9S, etc. You learn throughout the story of NieR as well why it was she behaved the way she did; 2B forcibly restrained her emotions in hopes that she wouldn't get attached to 9S, and 9S wouldn't get attached to her. Of course, in the end, they still got too close to each other. This is one of the things 2B hints at right at the start of NieR, with being trapped in a neverending spiral of life and death. Being constantly forced to murder 9S again, and again, and again. You can claim her personality is bland or bad, sure, as it is subjective (even if I have to disagree). However, calling it underdeveloped of all things would certainly be a mistake. Outside of NieR, 2B certainly is mostly popular due to her looks, but to everyone who has actually played the game, she's certainly popular and resonates with them for more than just a pretty face and the way she looks after self-destruct.
But if it's her looks you're upset about, blame the designers. They wanted it, and Yoko Taro said "if you're gonna do that, then you better damn well make sure you make it the best one out there or else you're fired." Also, sorry for the long post, but I was @ ed by
Good Guy Giygas