If a professor tells you to not do X and you do X you're very clearly not doing what he says, whether that is 'cheating' who knows. A degree is largely a check mark on a check box for a perfect little life of doing what you're told. Now, if people think that having a degree means X then they are free to do that and will reap the consequences.
Honestly, why should the students bother to come up with original work when the professor can't even be bothered to create original tests? Why is it not 'cheating' for the professor to use another persons test?
Obviously, what's on the test was taught in the class, so why not use an abridged format of the information that makes it unnecessary to learn information not relevant to the course? The test is the subset of the information taught that is relevant to the conferrance of a degree. To know more is to waste your time.
In other words, you should do the bare minimum to get by. Well, everyone's motivation for getting a degree is different, and you are welcome to this opinion. However, if this is also your life philosophy, then I think you may be disappointed.
Now, I personally agree that this instructor was lazy. However, in a perfect world actually every single iteration of a class would use the exact same exam. This ensures that every student who ever takes the class is graded in the same way. However, some students retake the class and share exams, so this is not possible.
It's like if you're a magician and you have an awesome magic show. Why make up a new show for each new audience? If the audience is different each time, then your show is still awesome - even if it doesn't change.
What if the professor says not to review past exams, because he may use questions from them. You still say it would be okay to use past exams to study? Well this is similar - the test bank says: students, do not use this to study. Obviously the teacher should have made up his own questions, but the students definitely knew better ...