I'm pretty sure this is a purposeful "feature" of security at least for North America. They don't want anyone getting comfortable with the process and constantly make changes to ensure this. I'm not sure what this is supposed to accomplish other than to make air travel less comfortable.

I recently flew and the airport had gotten the new scanners since the last time I had gone somewhere. The signage was confusing as only some of the lines had signs that specifically said you didn't have to take out your electronics on "this lane only". Even with the new scanners they were pulling out half the bags for additional screening and only had one person doing the additional screening.

Coming back from overseas I saw how it was supposed to work, walked up and they directed me to a line and a specific bin loading station, had someone remind me to ensure my pockets were empty, walked through the scanner and my bag was already waiting for me, took all of 2 minutes.