The law is not automatically the best fix for all kinds of bad behaviour, and in many cases it clearly isn't, but I think this is one of those cases where it really is. Dramatically raising rent prices on someone who is already living there, is taking of a situation where the other party cannot simply refuse the offer, because moving every year gets really expensive quick. With many other kind of subscriptions, if the vendor suddenly doubles the price, they're easy to cancel. But not when it's the place where you live. It's taking advantage of a kind of vendor lock-in. A kind of monopolistic abuse.
And it's exactly the kind of thing that many countries do try to protect tenants from.
And no, the problem here is not pent up demand for building. That would be a likely cause when it's the initial rent for a new tenant that's too high. That's a sign there are simply not enough houses and too many potential tenants. But when the initial price is low, the landlord clearly does want to rent it to you. And when they then dramatically raise the rent, they're taking advantage of the power they have over your living situation. Preventing that by law is entirely reasonable.
