alt Hacker NewsMini diggers are cheap to rent for a few days on a job and you can shift absolutely tons more in a single day than a labourer can do in a whole week.
If a roofing company can complete three jobs in a month compared to one job without a goods lift then renting one for each job makes economic sense, especially if it's physically easier too.
I agree, should have mentioned that it must help productivity too. I was just surprised to see it on even the smallest building sites, like a 2 story house, where I thought the bother wouldn't be worth it.