That’s because it’s not an economic policy but a humanistic one. Stable housing should be a right. If rent control was the default, then obviously no renter would vote for arbitrary rent increases in exchange for maybe, someday in the future, rent going down due to increased housing supply.
It's not humanistic, it's pandering to current renters at the expense of everyone else.
You can put your right to stable housing next to your right to internet, healthcare, and every other meaningless positive right.