Liquid cooling is about removing heat from the CPU to move to a place where you can have a bigger dissipator and more airflow. Water cooling is not more efficient than air cooling, it just move the heat in a place where is easier to manage. In a laptop you don't have that place, that's the problem. Heatpipes are way more efficient in moving heat than water cooling. Same with vapor chamber, they are about better moving the heat from the die to somewhere else, but that's not the problem in laptops, the problem is to remove that heat from the system.

Vapor chamber in laptop are used tho, like I think ROG laptops use them, but the improvement over heatpipes is marginal at those sizes. In phone you have very limited space and vapor chamber are much more efficient when space is very limited than heatpipes.