If the transaction was unauthorised (i.e. the collection does not relate to the signed mandate), the payer can ask for a refund up to 13 months after the direct debit.
The difference is often your bank. Some of my banks don't even have a way to initiate the charge back process (you have to write a free form email), presumably to reduce overhead and to avoid losing cases needlessly, while the others make it very easy with a web form.
Charge backs are not only intended to solve card fraud. It's the most convenient tool you have as a buyer to deal with seller fraud. If you have good evidence, you can win them consistently.
Nope, before the modern approach to shipping stuff you simply couldn't get many different things unless you were in a big city. There weren't humans doing the route planning, there was no one because it wasn't worth doing at all.