I always do it myself because they tend to be a bit brainless when it comes to packing things. Some people don't even realise that heavy stuff should go at the nbottom of the bag!
I'm a bit sad about the whole packing issue!
I have to put similar tings together on the belt so they all go through at the same time... e.g. household cleaning things, refridgerated bits, fruit and veg. Then it is easier to pack at the other end.
My husband thinks I am as mad as a biscuit and can't see the merit of my system at all.
I know it is extremely anal of me... but somehow when the rest of my life is in chaos I can at least feel my shopping bags are in order!!
especially if there's a BOGOF or 3 for 2, I have to
make sure they're together even though I know it makes no difference
when they're scanned!