There's good reasons to having a dedicated, more limited device.
What bothers me is that the device is a hard requirement for students, which means TI and Casio get to charge unreasonable amounts of money for these calculators that are not reflective of what they'd otherwise be worth. I brought up the Chromebook not so much as a suggested alternative, but as a benchmark for what sort of hardware you can get for the same money when your market isn't completely tied to your product.
The Game Boy Advance SP had a reflective screen with a toggle-able front light. The Game Boy Advance, and all other Game Boys before it, had unlit screens.
Our exams in engineering school took into account we could solve 5 equations/unknowns problems with our TI-92 Plus (at the time).
Can't imagine students with Chromebooks during exams (edit: or maybe I'm just from a different time)