Why do men keep the Phone numbers if they are NOT interested?

if i am NOT interested i delete their number, i delete anyone s number so they won't contact me. If a guy claim to hate a girl and asks HER to delete his number instead of doing it himself and he refuses to delete it when you ask him but he doesn't want to see you, what is he trying to imply? He has a girlfriend by the way, so why keep it? he hasn't deleted my number in a year by the way, he just won't do it.
Why do men keep the Phone numbers if they are NOT interested?
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