Because the landlord got there first and staked a claim to the parcel of land, that they then don't use themselves for anything except charging others for the privilege of using it. I mean you can see how it's not a super compelling arrangement even though landlords have made it impossible to avoid in desirable areas.
Someone paid to make the land useful for you. They cleared the land, built a building, added utilities, and made it convenient for you so you didn't have to do all that yourself.
