This particular miracle was done for the Disciples benefit. I was done in terms that a long time fisherman like Peter could most understand, that there is no other way than supernatural for this to have been done. The immediate effect on Peter was that he realized his sinful nature.
This is one of those curious passages that calls for further examination. We might be too quick to judge here without knowing the fuller context. Is it something about these particular lame and blind? Is it that the Jebusites were using them as a defensive shield? Was this sanctioned by God? We are not told of David loathing lame and blind anywhere else in fact we see David going beyond the call for Jonathan's lame son.