Japanese culture may have an influence. There are various proper nouns in Japan. Nowadays, it is common to use it regardless of gender. When I was a student, there were quite a few girls around me who used me. This is because the proper noun 僕(boku) is often used due to the influence of anime, and many girls think that it is cute(kawaii). i don't use it in social situation, but I think it is a word that can be used by various people as a proper noun in everyday life. I'm not good at English, so I'm sorry if it is difficult for you to understand my English!

I think it is because some females in Japan want to show that they are not weak and can be treated like a strong, brave person, just some features we use most to describe a good man. In the past days, the status of females in Japan was much lower than males. I think now they don’t want to admit that they are born to be inferior to males. So they use 僕 to show their attitude. And also, there are males in Japan who use あたし(女性用語)more, because they want to show that they are cute and want others’ protection.