You fail to realise that in a lot of the cases the landlord is also the tenant. Anyone who owns a house or condo is a landlord... cutting the landlords income for a month is a big problem.
It is to fundamentally misunderstand the notion of what a landlord is when you consider someone who is simultaneously a tenant.
You cannot charge yourself to rent space you own.
They may occupy a space in the building but that does not make them a tenant. A tenant is someone who rents precisely because they do not own the space