I generalized this.  @mikehearn mentioned that no miner has, to the best of our knowledge, ever done mempool transaction replacement based on fees and that doing so would make Bitcoin less useful as a system, which would likely reduce the real value of bitcoins and reduce the miner's profits in turn.

In addition, there are other attacks, such as broadcasting two versions of a transaction simultaneously and hoping the merchant sees the one that pays them while the successful miner sees the one that returns the payment.  Since there are even more possible attacks than this, I think generalizing it to be less specific about the methods of attack makes sense---especially since we can't be specific about the probabilities of any specific attack.