No, you are wrong I'm afraid - landlords are not in the business of evicting good tenants for no good reason - there is simply no reason they would do that other than genuine reasons like selling up etc. Even bad landlords will want to hang on to their good tenants. Don't believe all you read in the press, its largely only bad tenants that get evicted.
If a landlord needs to sell or re-occupy his property, then they are two very good reasons to ask the tenants to leave - we do after all still have lawful respect for private property rights, despite the certain sections of societies desire to undermine these bedrocks of civilisation.