While that's true, it's still not a simple issue. If you look at the whole it looks like a big, pervasive problem, but having worked in several jobs in financial positions I can tell you that none of them used gender as criteria for salary. If you were in position X, you made $Y regardless of your gender. So it's largely not the case that men make more than women who are equally qualified and employed.
So what's going on?
First, many women stop work to have children. This interrupts their career progress, resets their salary, and prevents them from ascending as high as men. This is the reason that women who stop work to raise children and later divorce still get alimony. There is also a perception that women will do this, of course, and that is a problem.
Second, the careers that men choose tend to pay more. A carpenter, an electrician, a plumber, an engineer, a doctor, a tool and die machinist, a computer programmer or administrator, etc. The careers that women choose tend to pay less. A teacher, an administrative assistant, a nurse, a librarian, medical data entry, child care. Now the reason for this is actually pretty complicated. Professions that men worked were paid a salary to support an entire family wife and kids. That amount of money was simply what a man cost, since any job he took necessarily had to support his family due to cultural standards of the day. If he wasn't getting paid that amount, then he could neither support his existing family, nor could he marry a woman and start a family. Professions that women worked were paid a salary to support a single person or possibly a single person with one child. Today, those salaries remain affected by those historic amounts due to market forces. That's why professional jobs designed to attract men have reasonably good salaries even if they largely didn't exist when the workplace was divided on gender lines (i.e., computer programmers).
The key to take away here is: women and men are voluntarily choosing their own professions and we still see a salary discrepancy. The professions they choose have salaries determined by market forces, which includes how people were paid in the past. Programs exist which encourage women to take college paths that lead to better paying careers, but in spite of the fact that women now consistently and significantly outnumber men in annual college enrollment numbers, men still outnumber women in technical and professional degrees and women are still not choosing degrees which result in better paying careers.
So who is to blame? On the one hand you have people saying that women don't make as much and that's a problem for society as a whole. Women are also not taken as authoritatively as men are, so men tend to get hired into positions of higher authority which, of course, pay more. On the other, you have people saying that women made voluntary choices that resulted in them earning less so they should bear the responsibility for the consequences of their own choices rather than expecting society to fix it for them.
Fundamentally, none these problems can be easily solved through government policy or regulation. Are we expecting the government to step in an force salaries for jobs to be increased or decreased? That you have to pay a teacher and an engineer the same? That's not equality. That's parity. Are we going to say that the woman who worked 5 years, quit 10 to raise kids, and then returns deserves the same salary and opportunities as a man who has worked for 15 years? How is that fair to devalue 10 years of relevant experience? What about the increasingly common situation where the man quits his job to raise the kids? Does he deserve the same considerations?