to expect my mum to say bye before ending a phone conversation?

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I genuinely don't know if IABU and happy to be told that I am.

My mum, when she is on the phone to me (I don't know about how she speaks to others, although she does do the same thing to my DH), if the conversation is coming to an end or if if I say that I am busy right now (she calls me at work), without saying "OK bye, speak later" etc, she just hangs up. I always find myself saying bye to a closed phone line.
She calls me almost everyday at work and I've only ever mentioned this to her once or twice, latest yesterday when I texted her saying that hanging up on the phone is rude.
She doesn't hang up to be rude, I know that, she just thinks there's no point in talking further, so just puts the phone down. It irritates me.

AIBU to point this out to my mum? One one hand she is 71 and is my mum and who am I to tell her how to make phone calls, on the other hand, it is irritating, but ofcourse it's not a big deal really and I probably upset her when I pointed it out and now I feel like a bitch for taking offence at it.
Oh well...after writing that down, I probably am being unreasonable.

My DM may be related to some of these parents. She calls me then says, 'oh, hold on while I just sort out the dinner, the spaghetti is just coming to the boil'. Then quite often she will instigate a conversation with someone else in her house while I hold on like a lemon.

Or she doesn't call me for ages and I make all the calls. If I mention this she says she doesn't call because she never knows if I will be in.

Yy to teaching my mum to hug. She's much better at it now.
Yy to MIL with no hello. My DH rings her, she answers and launches Into a long monologue instantly. So if he actually needed to ask her a question (hence the call), he has to wait about ten minutes before she stops talking. I always know when he's on the phone to her because he's not saying anything :)
Another family member does the hanging up thing with no bye, also doesn't speak when he answers, just remains silent. So I don't ring him.