Good point. Why didn't Jesus turn the other cheek here? (I ask this in all seriousness).
IMO ... it was a time to show justice. It was a time to show the people the error of their ways.
As a father, do you discipline your children (or are they too young still)? I'm not talking about spanking, just discipline in general.
Turning the other cheek does not mean doing away with justice. There are consequences for our actions ... both good and bad.
However, to answer your question, I think he did it because it was an effective way to teach what needed to be taught.