So, devices are built less around discrete components than they used to be, but there are still tons of discrete components in any given product, and these discrete components fail more often than you might realize. One common failure is failure of jacks/connectors--sometimes the solder joints get ripped out due to stress.

However, I think that you're basically right anyway... because when you pay Apple for a laptop repair, I think there's a good chance that they do a logic board replacement or something similar. The logic board itself is made of components and can be repaired, but it often isn't repaired, just replaced.