It's a sadly outdated social norm that sees all rodents as "cheap, replacable pets that sit in cages or hutches and do nothing all day".
It's only in the last decade or so would be my guess that people have started to realize cage sizes were too small and that these creatures offer a wealth of love and bonding if people just take the time to interact with them on a daily basis.
I cringe when I think back to how friends pets and even my own lived when we were younger. In fact I had a cousin who had a rabbit that lived in a teeny tiny hutch all alone in their garden.. even in winter. Back then it was "normal", now as adults we see it for what it really was.. outrageous. That poor bunny must have been SO LONELY nevermind cramped and cold. Did it ever see a vet? no, did it live long? not that I can recall.
Another family member had a hamster in that horrible overpriced rotastak circular cage (The one that was THE CAGE TO HAVE at the time). So so so cramped. They never played with it as it was a biter and only ever took it out to clean the cage.
When I look back at my very first rats years ago I honestly shudder at the tank they were in, not only was it too small but no hammocks (they just didn't exist then!) and very very few toys. It was basically "Here is your bed, your horrible muesli food and your water..oh and you have to share with your friends." That does not mean I was a bad owner, I was just doing things the way almost everyone else was back then.
Does it mean the family and friends who did the same were bad? no.. it's just what we all knew at the time.
For some they still live in that old reality passed down from parents, for others like myself we evolved into a more humane way of pet husbandry.
It does infuriate me though when people say they won't take a pig to the vet as it only cost £20. That's just nonsense, completely illogical. How much does a child cost? Nothing, so why bother spending anything on a kid then!
Oh and
@Jaycey to create a child might cost nothing, but once it's little heart starts to beat it will cost you more than anything else in your world

But I do get what you are saying and agree that animals should not be denied medical treatment just because they are animals regardless of size.