Often times they pick a starter name that ends up not fitting or people in their private lives keep outing them. It's usually not a big deal. There are outlier cases but usually with those cases most people know that those girls have many other issues going on (someone that just got banned on Twitter comes to mind....)
It could be either, every case is different. A few girls do it to avoid stalkers, so that's completely understandable. But then there the girls with bad reviews, so that would be a red flag.