The government also has people who audit contracts looking for places where the contractor has committed a technical breach. In my experience breaches on eithe

The government also has people who audit contracts looking for places where the contractor has committed a technical breach. In my experience breaches on either side tend to get netted off fairly amicably. I might swap you a change request that you want for signing off a performance deviation I can't avoid, that kind of thing. However the contract still serves a purpose - it provides the ground rules for that kind of trade. It does sometimes happen in bad faith (usually when the contract has a long and sticky history already) but most of the time it's just a more formalized version of goodwill. And that formality is necessary when you are talking about millions of dollars per change.