Soldering down the ram uses less vertical space (thinner laptop by a few mm) and less planar space (smaller PCB). This lets them make the laptop marginally thi

Soldering down the ram uses less vertical space (thinner laptop by a few mm) and less planar space (smaller PCB). This lets them make the laptop marginally thinner and have more space for other things (mainly batteries). If you look at the smallest form factors in consumer electronics (cell phones for example), nearly everything is soldered to one board in pursuit of reducing size. Realistically, Apple would not be able to make their laptops as thin as they are without doing this. That being said, it does provide them with the nice side effect of being able to extract incredible margins on hardware upgrades. Edit: Missed the point that we are talking about desktops, same idea still exists, it lets you make the form factor smaller and it requires less space since you don't need the connectors and you can be a bit more creative with the chip layout.