Hi Ian, you're right about manufacturers not stitching their customers up with bad advice, they'd see a lot of warranty returns if that was the case. However, having done extensive testing they will be confident that under normal working conditions your engine will happily run to 10,000 kilometers (if the user manual says that) before needing an oil change.
Will your motorcycle benefit from more regular maintenance? The answer is, of course, 'YES'.
Ideally we'd change oil and filters every 4,000 to 5,000 kilometers as you said. If you grab yourself a re-usable K&N air-filter you can every year. It's Hygroscopic and attracts moisture, which will turn to acid and eat away at the master cylinder and caliper bores. You shouldn't need to change spark plugs very often, unless you own a carburetted engine and are partial to flooding it. Obviously thinks like tires, brake pads, and the chain need to have a constant eye kept on them.
I've just been looking through the owner's manual of my motorcycle and noticed that after the initial oil change at 800 kilometers, Honda recommend changing the oil every 10,000 kilometers.
I know Honda wouldn't tell me to do something that would hurt my motorcycle, but this does seem like a long time to wait for an oil change. I have only covered 8,000 kilometers but decided to change the oil anyway and to my surprise it was disgusting compared to the new engine oil I put in, way blacker and thicker. I have now decided to change the engine oil every 5,000 kilometers just for a bit of insurance and wondered it there were any other areas of the motorcycle that might need or benefit from more regular maintenance than the owner's manual suggests.