On a laptop it's not very practical.

Because you can't swap the motherboard, your options for CPUs are going to be quite limited. Generally, only higher-tier CPUs of that same generation - which draw more power and require more cooling.

Generally a laptop is built designed to provide a specific budget of power to the CPU and has a limited amount of cooling.

Even if you could swap out the CPU, it wouldn't work properly if the laptop couldn't provide the necessary power or cooling.