Maybe I have an over-simplistic worldview, but it seems to me that the public risk created by illegal business practices -- not just the provable harm actually caused -- is a strong factor in determining the appropriate remedy. Business laws and regulations exist for the purpose of protecting consumers from unethical practices and to minimize potential damage to the public generally (i.e. adverse economic impacts). We have all seen what can happen, for instance, when there is not proper oversight and enforcement of regulations in the banking industry. Persistent, repeated failure to stay within the boundaries should result in severe sanctions.
If a lawyer misuses client trust funds, the lawyer is subject to discipline, regardless of whether the funds were later replaced. If the lawyer does it repeatedly, disbarment is appropriate. The privilege of having a law license has been forfeited. Even though no actual harm may have occurred, the lawyer's actions, if unchecked, have created a substantial risk of harm to the client, and to the public in general if others follow suit.