Power and budget constraints set for the laptop. If they could afford it, they would've add two. TB3 controllers are bulky, more power-hungry, and expensive. T

Power and budget constraints set for the laptop. If they could afford it, they would've add two. TB3 controllers are bulky, more power-hungry, and expensive. The reason TB3 is so fast without using up too much CPU is that its controllers handle most of the processing, not the CPU (bulky/power hungry). They're expensive because only Intel is offering the controller at large scale that companies need. USB 3.0 and USB 2 do not need such a large controller, they offload to CPU mostly and you can buy it from anywhere, so they're cheap too.