back then -- largescale wireless also didn't quite exist yet.
It is not because other calculators might be more powerful. Primarily, it is because TI has paid or schmoozed the right people. Officially, the word is that they cannot verify that any other calculators do not include internet or phone network access, and maybe a handful of other features. But at the same time, I have never taken a test that allowed you to bring anything you wanted; Tests are too much about memorizing the material for it to be feasible to allow text books. And when they do, it is only because the test is designed that unless you are an absolute expert and memorised everything, you will not have time to finish.
Remember to say hello to your bank teller.