The only situation in which I would want to be told about one’s exes is if the person is/was poly and their exes or present partners include people they live with, work with, or regularly spend time with especially overnight time under the same roof.
It’s an awful feeling to watch someone interact with people and be physically close with them and wonder whether they’ve slept with some or all of those people and know the answer is probably yes, and that someday someone else will be standing in your shoes looking at you thinking the same thing.