* Feminists really do fight for representation in these jobs to the point where one of the largest sexual discrimination lawsuits was brought up by women trying to get into the coal mining industry.
* Women already have significant representation in such jobs and especially in other low wage jobs, such as textile manufacturing (in sweatshops, for instance), nursing, fast food work, oil drilling, childbirthing (and other thankless reproductive labour), janitors/sanitation etc.
* These jobs are generally seen as undesirable anyway, and there isn't a social push for men to enter them. It's expected that with less push for dirty (and trade) jobs in general, there would be less of a liberal feminist push for them too. This is consistent with the fact that second wave feminists argued for any involvement of women in the workplace, even blue collar jobs, but now such activity is less prominent.
* It's a class issue too, and the perceptions, biases and elitist attitudes which prevent entry to such jobs for both men and women have been challened by intersectional and Marxist feminists.
* Part of feminism is challenging essentialist and elitist narratives about women and their capabilities, which managers in such industries cite in arguments against hiring women
 Sean Sayers, "Marxism and Human Nature" discusses this elitism at length as both a gender issue and a class issue
I used the word 'push' because I was responding to a comment which identified 50/50 representation in all occupations as potentially a reasonable goal. It would surely take a big push to achieve gender parity in garbage collection, which is 99% male in the US!