What is reasonable to expect of retired grandparents?

I don't think there should be any expectations at all.
I mean it's sad the kids don't have a the relationship you'd like with your parents but sometimes that's how it is. I was never close to my mum's side but close to my dad's side.

You're assuming a lot here. There's no indication the OP has done any of that.

That’s total bullshit, I’m sorry for you. Fair enough not committing to a regular event but occasional babysitting is the minimum they should be offering you. I’m sorry you don’t have the support you deserve.

The double standards of MN.
Todat's parents are encouraged to set boundaries, dictate who can and can't communicate with the children, micromanage all human intervention and 'go lc or nc' at the drop of a hat.
Yet when the granparents don't fall in line or are not that interested, it's them that are unreasonable.
They didn't ask to have grandchildren.
I am not saying this is the case here, but there is going to be a lot more of this in the future. You can't treat your parents the way MN often encourages you to then expect them to bounce back when you feel like it. You reap what you sow.

I have a good relationship with my mum & dad so Id be saddened if they weren't interested in my kids. Not to the extent I expect childcare but my parents will always want to know about exam results etc (they would send "congratulations!" cards)

Do you ring them regularly and chat? Do they ring you?

I'd be very disappointed if they lived that close and took so little interest in my family. As already asked, it would be interesting to know what their own parenting style was when you were a child. Did you have actively involved grandparents? Also, do you have siblings and are their DC treated the same way.

I think I'd match their energy and leave them to live their lives. Hopefully they won't suddenly find they need you in years to come when they're in need of any form of care.

You'll probably get told you are selfish and self absorbed arsehole and no one owes anyone anything as thats how these threads tend to go.

But i think yanbu and this is really sad and this isnt how family should be.
And its okay and reasonable for you to be sad about it and feel a sense of loss.

My mum was my rock when both my kids were newborns. All my family help each other out (goes both ways) we're the only ones in the uk.
My aunt drove 3 hr round trips 2 days per week for about 6 yrs to look after her DSs kids. They dote on each other and are very close to her as teens / tweens and there are 3 of them 🤯 so she had her hands full.

I get untold joy from seeing how thrilled the kids are to see my DM. They run to the door and my ds looks soooo pleased when her gets to settle in on her lap and watch a bluey.
She finds it hard these days as her health means she can do a lot less now so she generally doesnt babysit or look after them solo now. Thats my choice to protect her health as they are 2 and coming up 4 so high energy. She does help in a pinch if oldest is sick and we need a day.

There shouldn’t be expectation, but it’s reasonable to be very disappointed by their lack of interest. I agree, match their energy and see how long it takes before they notice. Some people are just uninterested in anything outside their own immediate bubble. They often end up very lonely.

It's very disappointing and hurtful OP. I would try to start matching their energy and not really caring what they do.

For me there should be no expectations, you need to not place expectations on others.

if someone offers or wants to do stuff with your children or to baby sit that’s lovely, and yes it’s shit that they don’t want to be more involved, but no, you’ve no right to put expectations on them, you can ask, if the answer is no, as disappointing as it is, you need to accept it.

I think that's piss poor of them and I'd be disappointed. I don't think that anyone is entitled to free childcare but in general I believe that when you care about someone then you make time for them.

What was their patenting style like when you were growing up? Do you siblings/nieces and nephews?