Asking of your current salary by interviewers fulfills many purposes for them and it also gives you a chance to show your self-worth.I can explain.

Why does every employer ask about my current salary during a job interview?

Everytime I have a job interview or ask a friend about one of theirs, eventually the employer asks about current pay. This happens independently if I sent a CV or if they got in touch with me first. Why is that?

Answer: Just to get you as cheaply as possible.

Thought experiment:

Interviewer: “What’s your current salary?”

You: “It’s twenty seven thousand five hundred”

Interviewer: “Great! In this new job, you will receive one hundred and fifty thousand. That seems fair given the role. And as our profitability, sales pipeline and market positioning all do not depend on you alone, there is no reason to vary away from what the role is worth to us”

Sound likely? Ever heard it?

Me neither.

I don’t have good advice though.

I’ve always mentioned my current salary, and then been surprised to receive something almost entirely similar within ten percent.

Because I know a little about software, but am otherwise quite stupid, really.

Source: https://www.quora.com/Why-does-every-employer-asks-about-my-current-salary-during-a-job-interview