Coming north into the US you will get scanned plenty. There's license plate readers, facial recognition, and your name will be entered at the CBP booth either manually or RFID before you even reach the booth. Going into MX at San Ysidro CBP does have southbound booths and plate scanners, I assume facial recognition. I have never seen the booths staffed in the last five years, but have heard from others they do periodically. Coming north into the US at San Ysidro it can take hours in line if you don't have Global Entry.