Blowjob to most boys/men are about using the girls/women or showing them their places, at least secretly they think like that, in their boys group chat, they discuss that. So, even if a girl/woman is told by their male partner than they want bj bacause it's fun, why should she believe them? And, many girls and women find it disgusting. Why force them to perform it?
Many people are not about enjoying the sex, they just have intercourse for children. If you criticize such women for not giving bj, then that is insane too.
In a word, let it be a woman's own choice.