Because a Raspberry Pi isn't going to run a neural net all that quickly, and sometimes you have to throw computing power and ingenuity at a problem,
like a Movidius Compute Stick.
Yours truly bought a stick. It's not actually a 'Movidius', but a 'Neural Compute Stick II'.
I guess they are trying to move away from the Movidius name or something.
Hmm .. bit soon for conclusions.