You can actually see that in many of those cases all of those short belts/rollers are actually funneling different major sub-assemblies together. Because you ha

You can actually see that in many of those cases all of those short belts/rollers are actually funneling different major sub-assemblies together. Because you have lines coming together the conveyer/rollers provide a bunch of benefits: a) It's a short term buffer. While the lines are going to balanced pretty well, it's still super useful to have a small buffer. b) Lets you spread out the lines a bit, giving you more flexibility with the design and layout of your lines. This is probably one reason why they don't try to pack the lines closer so that you can just hand off. c) Having people shuffling the parts around is just inefficient. You don't want to hire a person just to shuffle the parts over such a small distance. You don't want to interrupt the last guy on the line's job with such a task. You could try to minimize the cost of runners by batching up your work before moving them (and having your runner rotate through different things to haul), but now you introducing probably more buffer than you want, and also potential latency spikes into your process.