The thing is many of these companies who have been gifted contracts, pass most of the work on to others anyway, as recently they have been so enormous, that no one company can handle the work. These companies are generally already on the Government contract preferred list, and therefore in an emergency are first call companies. If you already have a contract running, much quicker and easier to extend than to go through a process from scratch.
Now, I accept this doesn't always mean good value for money, and there have been some deplorable awards on contracts to companies with little or no experience, and this is being called out in by consultancies and the companies they employ.
What you never hear about is all the good work that has been going on quietly in the background by the thousands and thousands of private contractors who keep government, and in particular, the NHS running.