> part of the reason they don’t lower rental prices is because it’s hard to increase it later

At least in the US this happens due to rent control rules. When the landlord knows that once they lock in a renter they won't be able to raise prices much for an undetermined amount of time (what if the renter decides to stay there for 30 years!), they have an incentive to make the starting rent as high as possible.

If they knew they can raise prices when needed, they could afford to lower prices in a downturn knowing they can raise later.