That's just poor software. As long as the software and teachers or professors allow for going over answers and checking for correctness it should be alright.
That sounds like "My Math Lab" by Pearson. It is horrible like everyone talking in here states.
It's also a bundle with the book sold by unis, because the code 'allows' you to submit homework required for the class. So they're doing both resale prevention, AND horrible grading.
People I know who have to interact with it call it "My Meth Lab" - because you have to be high to like it.
