bullshit. Being difficult is the main reason. There are numerous studies that show why women choose the professions and careers they do. Sexual Harassment on the job, while certainly there, doesn't exist exclusively in jobs that require hard labour, or in greater amounts than an office setting. Your premise is completely nonsensical and not based on fact.
66% of women who work in construction experience sexual harassment or gender bias while only making 11% of the workers in the industry. manufacturing work has the 3rd highest rates of sexual harassment, is it that hard to understand that a woman who is looking to go into this field would find these studies and have that as their main reason to not want to work there?
then again most women just dont consider working in construction because they just dont see it as a viable option. why? because its male dominated. for most women the thought of working in construction would never cross their mind due to pre-established norms for that work field. if it helps you, think of the childcare worker industry. 92.3% are women and 7.7% are men. why dont more men work there? they just dont even consider working as one in the first place. construction is seen as a mans job and as such women dont think of working there. childcare work is seen as a womans job and so men dont think to work there.
the sexual harassment rates are the main reason as to why a women looking to work in construction would turn away at this point and pre-established norms for the workers of construction are why most women dont work there.