First of all if you go looking for the good tenant registrar you may find it difficult to locate, there is a risk involved with all tenants just as there is a risk for the tenants i.e nightmare landlord. the subject in question, the agent sent eviction notice to the tenant and then advised for the guards to be called in (and so the story ends unless we find out the contract involved).
Regarding what an agent does for their fee is generally take the hassle out of it for the owner. If the owner has the time and doesn't mind dealing with the calls and viewings then of course it makes sense to do it yourself. For a months fee you would generally be talking about a managed letting in which case the landlord has no contact with the tenant and the agent is responsible for ensuring upkeep and income are up to date. Your gripe with agents doesn't make you an authority on the subject you should be able to allow for the reasoning that letting an agent do the work is of benefit to some people.