No, you are not.
I use to save them for about 5 years, because that’s what my mom did back home. I never thought too much about that, just kept everything related to a month together and store it somewhere.
Until the day it helped getting my son into primary school.
The thing is, when you apply for a public school, they prioritize those who lived longer in the area around that school.
We have lived in different apartments since my son was born, but always in the same area. When we applied for that public school, we used the old utilities bills as proof of residency, and we were able to secure him a place in the school just across the street.
There were other ways one could use as proof of residency, but this one was by far the easiest and quickest.
Hence, no you are not silly for saving them.
You may thing it’s a useless, until they day it’s not.