Why does my ex girlfriend keep my phone number after she broke up with me?

[Anonymous]

I think the woman is mentally unstable. I dated this 29 year old woman twice. She says I'm a rarity among men and my parents did a phenomal job raising me, have all the qualities she wants in a man and other bs. She has 3 kids who are still very young. We broke up again about 4 months after the first break up. We broke up this last time about 10 days ago and just last night I got a call from her number in which I did not answer or call or text back. I'm pretty sure it was her daughter as she has contacted me before, quite often. But I'm wondering why she still has my number as she said she is no longer interested in me, doesn't see a future with me and such. I don't text or call her, I'm already passed that childish behavior but why does one still keep the ex's number?

[Anonymous]

I kept someone's number because I care very much for him.
Yes, even love him.
Yes, probably came off as mentally unstable.

[Anonymous]

Well you guys seem to be very on and off, so I’d probably keep my ex’s number too.