Current processors are using less power than ever. That low power consumption is only rivaled by the fact there are two or more cores. If it weren't for those mulit-core processors, we could almost return to completely passive heat sinks. It's definitely easy to spot the better CPU coolers given that heat pipes are the standard.
However, the exemplary CPU coolers have quite a lengthy bit of heat pipes machined to fit certain shapes and sizes all hanging over your CPU. Some users don't mind these CPU coolers while others still like something a bit quieter and as cool as possible. This brings back, yet again, to liquid cooling.
Source: Virtual-Hideout