Surely it depends on the family dynamic?
I spent a lot of time one on one with some of my grandparents. I would visit them on my own. Other grandchildren did it didn't, depending on their own relationships with them. If they were still around today, I would definitely still go spend time with them. My siblings/cousins wouldn't necessarily.
Now, I'm not saying I should get any inheritance or that other grandchildren shouldn't. But different family members have different relationships. I have a bond with one of my uncles that my sister doesn't (and no, nothing untoward, my mum's family is younger than my dad's so I spent time with my dad's brother and his family as a child, whereas my younger sister was more often with my mum's side). When we eventually lose him, undoubtedly my sister will be sad but for me it'll be like losing another grandparent. My mum's sister is loads younger than her and is therefore more like my elder sister than my aunt.
To be clear, I do not want not expect any money from any of them. But what I do know is that my relationship with those family members will be considered differently to others nieces or nephews. By me and them.
Therefore, some grandparents may wish to leave something to grandchildren with whom they have a close bond. Others may see them as an extension of their children. And either is ok.