How could you not know this? Have you never seen another delivery driver? Do you really need a training video to tell you that when you need to carry a lot of heavy packages, you should use a dolly?
Yes, you need.
Case in point, in the last half a dozen orders I've made that involved a somewhat heavy and/or large package, not a single delivery service used a dolly or delivery cart, even on orders from a certain multibational furniture store.
You expect your employees to do their job safely? Then you explicitly cover the safety procedure during training, and you directly and intentionally state that it's in their best interests to do so. Otherwisr you can't possibly assume they will comply with an implicit rule.
in the last half a dozen orders I've made that involved a
somewhat heavy and/or large package, not a single delivery
service used a dolly or delivery cart
Dollies are inherently a mixed blessing. You can pile more stuff on them - but if you've got to get up a kerb, you've still got to be able to lift that weight, and the dolly as well, and keep everything from sliding off at the same time.
And it's not just kerbs. They've got steps up to their front door? Can't use the dolly. Old flat/apartment without a lift? Can't use the dolly. Lift needs a key you don't have? Can't use the dolly. They've got a gravel path? Can't use the dolly. They've got a thick-bottomed UPVC door frame? Can't get the dolly through it. On a steep hill? Dolly will make things harder...
And it turns out, in a city like London, there are a great many buildings with one or more of these defects - and the worse the parking situation, the further away you park the van, the more kerbs and things you're likely to need to cross.
Hence, even though drivers are issued with dollies and trained in their use, many deliveries are made without the dollies because they don't make things all that much easier.
How are the dolly's wheels any different from the delivery person's shoes?
Sure and the only ones to ever use a dolly are ones delivering home appliances
Partly because they are trained and know their craft - but mostly because they are correctly paid, and so they are almost always long-term workers with learned expertise at driving and delivering.
(As opposed to the Atlantic writer, who did the job for a day, didn't know how to do it correctly, found it difficult, and whined about it. That's not actually telling us much of anything, when you think about it.)