But if I recall correctly, the reason why needles rather than scanning is precision, speed and 2 two-way communication. Needles is a more risky and invasive procedure, but it does allow near instant communication, at the precise neurons you want to target, and it allows to override the signal.
In some cases of paralysis, the signal to move a muscle might be there, but it’s just to weak to get anything done. By amplifying it, you fix that problem at the source.