"rental contracts ending" is a cute way of saying "evictions" and a way that allows you to mentally distance yourself from the messy gooey people problems that arise -- grandma getting thrown out on the street, communities being disrupted, etc.

I'm generally against rent control, but I still acknowledge that housing is more than a technical business contract.

It IS exactly just that to some people, but if you refuse to acknowledge the people on the other end, the only people you're going to bring to your side are your buddies at the country club.

Legal expenses, if the eviction sees court challenge. Especially if any claims of discrimination are sustained against the landlord. Also, labor cost of emptying the unit, repair/cleaning to make the unit ready for a new tenant, etc. Folks being evicted usually aren't in a cheery mode about it, so stuff might get broken.