Historically (back well before the Internet) I often purchased service manuals direct from manufacturers, as a private individual, and from work - in fact I don't recall EVER been refused back then, with some even providing them free of charge.
The first refusal I did get was from Pioneer (who had previously supplied me many times), and that was the beginning of the end - from there more and more stopped supplying other than their authorised dealers, to the extent it's now very rare to be able to deal with a manufacturer unless you're an authorised agent, and often all but impossible to become an authorised agent.