Laptops don't have liquid cooling systems the same way that desktops do because they're not designed for them, nor would they be decent candidates for them due to physical limitations. That's not to say there's no liquid-cooling solution at all for laptop users; you can technically buy an external liquid cooler and set it up for your laptop, but it won't be anything like the built-in ones you might be acquainted with in a desktop computer. Those all-in-one or custom liquid cooling systems aren't constructed for portability; they have many parts, can sometimes be sensitive to impacts/placement, and are generally heavier than their dry counterparts. It can also lead to a quieter system because fans don't need to spin as fast to cool the components. When you do that, it essentially means turning your laptop into a mini desktop computer — defeating the purpose of owning one.