Because it’s not as simple as you’re making it out to be. This is highly workload dependent - you can’t just connect multiple CPUs that are designed to (even wi

Because it’s not as simple as you’re making it out to be. This is highly workload dependent - you can’t just connect multiple CPUs that are designed to (even with old hardware) have lightning fast connections to their neighboring hardware with a slow USB cable and expect it to just linearly multiply power. The CPUs end up actually running slower because they spend most of their time sitting around waiting for instructions to execute. This even used to be a problem with multi-GPU set ups, just much less of a factor. This is why cluster computing is far more dependent on software being able to distribute work and load balance than the actual hardware. There exists software where you can connect random devices together in your house over Ethernet and make a cluster. This is why every supercomputer is geared towards massive number crunching where you can break up the work into many smaller tasks and give each node a task to work on. Cluster computing sucks and is inefficient for anything resembling a normal workload.