There isn't much creativity involved in most recommendation letters. And frankly, that doesn't matter. The important thing to ana school or employer is that the individual who signed the letter believes it accurately describes you.
Yes, it would be nice if every letter was rewritten completely de novo. It isn't very surprising when it doesn't happen that way.
Don't worry about it. The worst that will happen is that they'll contact the recommender, he'll say you're a good candidate, and that'll be the end of it.