Refusing to answer a fact seeking question in a negotiation isn’t great strategy. it may not even help your case. if you make too little, that’s already your problem. Someone offering you more than what you make is a net positive. Withholding information leading to a whitheld offer does you no good.
I've had people say that they already had other offers well in excess of current pay, making current pay moot. It's not a fact seeking question in a conventional sense. It's just one method of trying to move the process along with least effort. If you give an answer then they can make an effective offer quicker. If you don't there may be more work, that's all.
Suppose you are just finishing a Ph.D. and took a few years off. Suppose you took a year or two to do freelance or work 1099. Suppose you went abroad to work for a year or two to take of your dying parent. These are all things I have run into.
Edit: One more good one. I've known people who won a green lottery or married an American citizen they met abroad. Showed up in USA with lots of skills having made much less in Eastern Europe.
