This recent headline from the Telegraph clearly identifies the current problem with the rental and probably wider housing market. The corollary "why become a landlord if you wish to be able to evict a good tenant" is worth considering.
The answer seems to be because of the historically excellent capital growth in residential property values and the differential in marketability and values between let and vacant housing. If the country is to create a stable housing market both rented and owner occupied, we need to continue the direction of travel in favour of long term professional landlords.
Why become a landlord if you can never evict your tenants?