On a modern bike with Cartridge bearings what ACTUALLY needs to be serviced nowadays?
Forks, Rear shock, Bleed Brakes, true wheels (is this part of a service), indexing. Anything else?
Replacing cables, pads; greasing headset or at least checking for play. Checking chain wear and replacing if necessary – ditto cassette, chainrings. Checking tightness of all bolts. Clean and lube transmission. Check straightness of rear mech hanger (and even frame or forks). Many, many bikes still don't have cartridge bearings (any Shimano hub for a kick off) – so degreasing and repacking those is a service job – which means removing rear cassette and having the right cone spanners.
I know most of this stuff is basic for regular riders but it's beyond a lot of less "serious" cyclists.