You seem to be mixing up providers and payers (insurers). Providers don't deny claims, but sometimes payers sent claims because the providers coded them incorrectly. There's nothing wrong with coding a claim with all services rendered and charging the maximum agreed rate. If the payers want a lower rate then they can negotiate it next time the contract is up for renewal.

Obviously it would be wrong for providers to bill for things they didn't actually do. That would be fraud. This part isn't in dispute.