Conor:
hours that are wasted sat there waiting to just get started to be loaded and tipped or waiting for paperwork? Certainly on the fridges probably half your working week if you’re doing Tesco and the like. When I’m on days doing our own store deliveries quite a few are on you with a forklift as soon as your wheels are stopped because they appreciate that hold ups have consequences for you but there’s far too many who just ignore you’re there and will be an hour before they start you and then take an age to unload you.
Cost externalization. It doesn’t cost them anything to delay drivers who aren’t on their payroll so why rush especially if they have drivers of their OWN sat there they just see ££ signs ticking away so they’ll tend to them first. Don’t ask how I know 
They’ll try to make it less obvious as ‘‘other’’ drivers will occasionally complain or threaten to leave without loading/unloading. I used to go to a place every evening, they’d always make me wait for 3-4 hours while they sorted out their own trailers. My company told me we can’t do anything about it as they’re our customers…On one occasion I did pull out after waiting for over 4 hours as I mistakenly understood my vehicle was urgently needed back at the yard for another run and got an ear full for it so blame your spineless boss for it if you’re regularly being kept for hours especially if it happens at teh same place/s.
When I was delivering to random large places (Tesco among them) at least once a week I would witnss a scnene where a driver was losing it threatening to leave etc. but the staff usually just shrug cause it’s none of their business. It’s a chain of idiots and the one at teh top looks at one thing only and that’s their own bottom line (financially)