I assume that this system was adopted to reduce the number of contracts. In the past, I believe you had subcontracts. You had every kind of contract, and you have fewer contracts now.
If you don't win a contract as a prime, then as a sub, you have to wait for a prime to pick you, if they pick you at all. There have to be a lot of losers in this game. There have to be a lot of small companies that have lost out in this game.
Are the savings worth it? How much money has been saved going to this system where you only have primes?