For one, women are more than men (slightly, around 51%, but more. And if not more, equal). So it's not true that "the small group tends to get less pay" in this case. Women are less only in some jobs (like IT). There are more women than men in others (e.g. in education it's over 60% women). But even in those jobs women might be paid less than men.

Second, women and minorities being paid less can be explained by many factors, from discrimination, to women (either naturally, or by nurture) not pursuing promotions/raises aggressively enough, to exploitation (e.g. since some minorities are in bad condition socially, or might be afraid of deportation etc, one can exploit that to pay them less, "take it or leave it"). These practices of course can not be the case with tabs/spaces.

Third, there are countries where the majority gets less pay. E.g. in South Africa the whites are paid more than blacks, same for other countries with a smaller more privileged citizenry and a wider base of rural/indigenous/colored/etc population.