One of the things that gets lost is that GPS units have a learning curve. Just like any other technological device in our society, the operator has to know enough to decide whether or not to follow the directions being given.
I have seen accounts of people following GPS intructions into wildly illegal and sometimes fatal misdirections, which points out that we can't just turn off our brains and follow the commands.
For myself, I drive a commercial truck and am in constant interaction with my GPS. Having a simple map display gives me a constant read on where I am in relation to the roads around me, and allow me to change my actual driving route quickly in response to traffic conditions. The interaction between local knowledge and the information given by the GPS allow me to get around town much faster than I would without it, or even by just blindly following the directions it gives.