They’re simply bewildered by it, just like the scientists in the 90’s who were also bewildered by THC’s less “totally psychedelic” brother. Because scientists as a group tend to find the reasoning behind things, they went about trying to determine what it was that the endocannabinoid system did, and more importantly, why it existed. For, as we all know, there’s hardly any space wasted in the human, or indeed mammal body, (excluding the appendix), thus there must be a reason for the endocannabinoid system to exist. 

This search through the body’s inner workings and how it responds to outside stimuli brought us to a couple of interesting conclusions. The first is that there are, indeed, cannabinoids that your body makes of its own accord, hence why the system exists to sense it. The second being that this system traverses throughout the body and is responsible for several different effects, even those not involving THC.