Associate
I think living under threat of losing your home with only two months notice, for no reason, pretty much covers it no?
A landlord can only terminate an (AST) Assured Shorthold Tenancy with a Section 21 notice (2 months notice after the upcoming rent day) once the fixed period has ended. At that point in the tenancy, the tenant still has more power because he/she has the right to terminate the AST with just 1 month's notice after the upcoming rent day. The fixed period can be set at any length. The legal minimum is 6 months but I have seen fixed periods of 3 years used. You can negotiate with your landlord for a longer fixed period, the one they give you initially is not set in stone.
If a tenant leaves 2 months after being issued with a Section 21 notice (no Court appearance) then he will not have a CCJ (County Court Judgement) on public record against him, even if he was a tenant from Hell! On the other hand, if he has to go through Section 8 (Court appearance) proceedings then there will be a CCJ against him. Hence, Section 21 can actually protect a tenant's reputation when the landlord just wants to cut his losses and get his property back. Otherwise, the tenant may struggle to rent another property if the landlord/letting agent does a CCJ check.
Furthermore, after living in HMO's for many years I know of several cases where landlords used Section 21 notices to get tenants to change their bad conduct. For example, where a tenant has repeatedly engaged in anti-social/threatening behaviour to other tenants, been consistently late with the rent, or built up a big debt for their energy bills, then the landlord would issue one but later withdraw it if the tenant changed their ways before the 2 months was up.
I rented for 15 years and only received a Section 21 notice once (because the landlord was selling up). If you're receiving them frequently and you did nothing wrong then consider moving to a cheaper part of the country where there is not the massive demand for rental properties which allows landlords to dump good tenants and then get new ones who will pay much more. Up here in the North East of England landlords are keen to hold on to good tenants, they don't want the hassle of advertising and a void period and running the gauntlet of getting a dodgy tenant if they can do a deal with a good tenant and have them stay on instead for a below market value rent.
Finally, if a Section 21 notice is legally contested by the tenant (which requires a Court hearing) then it will currently take at least 6 months to get the tenant out even if the S21 notice was legitimate. The landlord cannot just call the Police to enforce a Section 21 notice leaving date (even if they are in the right). It is landlords who typically get shafted and are left with no legal recourse when tenants don't pay their rent but continue to live in the property for many months after their eviction date has passed and then trash the property before they leave. The current AST system does little to protect landlords, but there is a great deal of legislation which protects tenants' rights.