Why do some parents choose savings over helping adult children?

[Perthgirl]

My Mum is a 86 year old widow has just received a HMRC self-assessment to complete. My father died 3 years ago and all of their ‘joint’ money became her money. She didn't want to pay an accountant to help with her self-assessment and asked me to help.
I have mentioned previously that she would need to complete a self-assessment but this fell on deaf ears as ‘no-one has asked me for it’.
She lives in a £700k very nice house and manages well on her own. She is fit, well and active.
We get on well and I think I am a very loving and supportive daughter. I have never received any financial support from my parents since leaving home at 19.
It transpires that she has over £500,000 in ISAs, Premium Bonds, numerous building society savings accounts. All building society accounts have the £85k IFA protected amount/limit.
My husband and I are 59 and 60, both work full time and have 3 children (triplets) in final year of university. When I did a rough calculation on what £££ she might owe, her comment was oh ‘I might not be able to afford to give the children their £50 Christmas money this year, as I will have a large tax bill’.
It is her money and she is entitled to do what she pleases, etc. She enjoys a very comfortable life, with 3 overseas holiday each year and a busy social life.
She has previously said that she has so much money coming in that she does not know what to do with it. My Dad had a very good state funded pension which she still receives. When I suggested that she might like to help the grandchildren through Uni, she said, well no, as I do not know when I might need the money for myself!
Why would some parents/grandparents choose to pay £1000s to the tax man rather than possibly help the family?
I realise that she may need to fund a care home at some later stage, but £700k + £500k = £1.2M.
Can anyone help me understand?

My mum's parents were so difficult to care for as they got older. They insisted my parents did the brunt of it and refused carers and homes. My parents were adamant that they would never put us in that positioning isn't to receive professional care as soon as it is needed, but this means they have ludicrous lump sum savings which may never be called on for care.

I intend to do more financial planning than they have and be a bit more savvy about tax free savings like Junior ISAs and PBs for grandkids etc . But I recognise that theirs isn't my money and so not my business.

I'd get up off my knees if I were you. I live 2+ hours away from my parents as does my only sibling and bar some light outdoor work which we all enjoy anyway, errands, etc when we visit, my sister and I have made it clear that we won't do anything that they can easily pay someone to do with their substantial stash of money. Something like going with them for an important hospital appointment where information needs to be conveyed? Yes. Cutting the large gardens or cleaning windows? No. They pay for things or they don't get done.

"Who said anything about uni costs?"
You brought the subject up at 18.51.

@Badbadbunny we don’t know if she has a state pension or if it is a full one. She is in her 80s. Many women of that age became housewives. We don’t know how tax efficient her investments are. Old people are entitled to days out holidays etc.
According to Google (AI) a comfortable pension is about £43,900 a year.

Yes, I used it as an example - the OP didn’t mention it at all. Good Lord.

Yes I know you're right about this. I get all annoyed about it and then they promise to arrange something that never materialises and we end up back at square 1. I need to stand my ground this time. They won't let me take over and organise everything they need.

Then you asked who brought it up. You brought it up.
You have sharp way and very little patience for someone just shooting the breeze on MN.

I really cannot assist with basic comprehension I’m afraid.

Maybe she thinks of it as continuing to support hospitals and schools etc. rather than “the taxman” as such.