I did until mobile phones became the norm, now I ask if they need her number to call. It made sense before phones were everywhere and you didn't make it to see everyone, but send a text yourself. My name isn't SMS.
Most people already have the number, the point I make in asking is to show them that I don't need to be their messenger. You can call my mother/father/grandmother yourself. If they're asking about my wife/kids, I'll just say "Sure" and then forget because I'm apparently a goldfish.
Most people who say "Tell them hi" are my parent's and grandparent's friends anyway. I don't give out a true friend's number, I agree that is not good.