It’s not your property they care about. They usually want this because it includes liability insurance if you damage their property or someone else’s, or your negligence causes harm to someone.

Renters insurance is primarily protecting the landlord. If you cause a flood, if a guest slips and falls and sues you, etc.

Your building would be fine if you found a renter’s insurance that didn’t cover your own goods (which would cost like $3/year less).

Renters insurance protects the landlord from liability claims. They don't care if you insure your own property, but I don't know of an insurance company that decouples liability and property.

Also, renters insurance is cheap, I haven't rented in more than a decade but when I rented I was only paying less than $100/year for it.

I just looked it up and currently the average premium for renters insurance is $15 to $22 a month.