When you sign a lease agreement, you get a guarantee that your rent will not go up during the term of that agreement.
So, if you sign a lease for $1000 a month on Monday, and on Tuesday the market rent for that area spikes to $10,000 a month, you’re locked in with a lower rate.
If I were a landlord in Oregon, given the above law, I would just only rent month to month. Breaking a lease becomes easy, but you also lose the pricing guarantee.