When you service your own car or clean the lawnmower or paint the house, you
don't need quality checks because you care about the result.
You own the car/lawnmower/house and because you own them you "care" about
them so you do the best job you can.
The key to quality is to allow the workforce to care about what they are
doing.
Well this hardly meets the requirements of the relevant customers.
As you're in the UK Peter, you're well aware that we have mandatory
MOT safety checks for cars (3 yrs + old) and that house purchasers
usually require an expert survey of any house they want to buy. This
is because we can't trust the 'workforce' or owners of these items
to be honest about their condition, or indeed trust them to 'care'
at all.