I agree and my pet hate #2 is Gottlieb pinball manuals - they ALL came in a machine and they 'should' (IMO) be made available for FREE download for this reason alone - but no, if you want one you have to purchase it and I think that STINKS!!!
Catch #22 - PBR are the main suppliers of GTB parts. when you order, you need to specify "Part number" and "Game". That's a bit hard to do if you didn't get the manual with the game ! I ended up buying all the parts manuals for GTB, Bally and Williams. But the game manuals should be freely available.