"Why can't we start with a phone that can be the CPU for wearables and tablets, and that can dock into a higher horsepower 'GPU station' with a mouse and a keyb

"Why can't we start with a phone that can be the CPU for wearables and tablets, and that can dock into a higher horsepower 'GPU station' with a mouse and a keyboard and a monitor when we need it?" Because a full-on SoC costs somewhere between $20 and $30? It costs almost nothing to add a full computer to any tablet/laptop form factor phone dock.