The subject of the poem makes it pretty easy for most people to relate to. For a lot of us, our grandparents are the first elderly people we know all that well. Hanging out with them gives us our first real understanding of the effects of aging.
Wrinkled and nearly blind she lay and snored (5-6)
The speaker doesn't exactly paint a dignified picture of his elderly grandmother. He could've chosen much more elegant language, but instead he just gives it to you straight-up. The truth is that a lot of times aging just isn't all that dignified, which is usually a very hard thing for the elderly to deal with.
Oh you think you're smart you young people,
she said, but I'll tell you you don't know anything. (27-30)
How many times have you heard an elderly person say something like this? Grandma Shmoop says it all that time, and it kinda drives us crazy. We've got to hand it to her, though, because in a lot of ways she's totally right. She might not know how to operate an iPhone, or even have a clear idea of what the internet is, but she's seen things we've never seen. There're things you just can't know until you've been on this world for a while.