In both cases there are gendered cultural associations built into the profession. Nursing is definitely viewed as feminine and software engineering is is still considered a masculine profession, although that perception is slowly changing as software becomes a more important part of everyone's life. Even if you get past that, the active shaming and harassment of people that enter or attempt to enter the respective fields keeps a lot of people out or drives them to quit.

The "men just don't want to be nurses and women just don't want to be programmers" standpoint usually assumes some immutable property (often genetics) that defends the status quo, and ignores mountains of other obvious problems that might lead to gender imbalances in a given profession. Obviously men and women are different, but there are many people that might enjoy and thrive in a profession they wouldn't otherwise consider because it's "not for them."