Why is it stupid? Because you will be inconvenienced as a landlord and not be able to intrude on the tenants with a knock? If a tenant can refuse entry, for ROUTINE maintenance, it gives them a bit of control. Already, landlords hold most of the cards in a landlord/tenant relationship. If you have a year lease, and the situation becomes such that you cannot comfortably stay (loud neighbors, for example), you must stick out your lease or pay for the time it takes to find a new tenant, as well as needing to often pay a percentage simply for breaking the lease.
It would be nice to have a little bit of the say in my OWN HOME as to who I have to admit, and when. There are times it is very inconvenient to have a landlord stop by. My friends and family call first, my landlord does not have to. That is just wrong.