Glad you asked this question. It's not about equal pay. It's about fair pay. I have seen people being exploited because they are not aware of the salary bands of the employer.
Quick question: if a caretaker or a maid comes to your 3 bhk house and says I will do all your household work for Rs 500 a month, would you hire him/her? If yes, it's exploitation to me.
There has to be salary bands (read minimum wage) for each role defined and disclosed by the org. Employers have an unfair advantage on the negotiation table. They know everything about the candidate, their last drawn CTC, their employment status. But the candidate doesn't know anything about what the compensation should be for the position.