You are hardly walking 'through' the shopping area in T1 to get to domestic departures. I always manage to quickly brush past WH Smith and then I am out of the shopping jungle! I have never been forced to go through the shopping area!
T1 is at times, far easier than T5, providing you know where you are going!
The second security check at T1 is done at T5 for domestic departures as well. However since you are already at the gate when this is done at T5, then perhaps we don't associate that wait as being linked to security since we are waiting at the gate anyway!