It activates the same chemicals in your brain as cocaine! 
Well, yeah, there are only ~~three~~^[@Neuromancer49@midwest.social corrected me] a few neurotransmitters. That's not saying much.
You know what else activates those chemicals? Practically everything. When scientists breed "knockout" mice without dopamine, the mice just stand there until they die of thirst, because there is no reward for.... living.
It contains more germs than a toilet seat! 
Germs like moist surfaces. We don't want germs on our toilets, which is why we make them out of porcelain, which is hard, dry, non-porous, and easy to clean.
If it had more germs than your colon, then I would be concerned.
Dopamine does a lot in the brain. Much of its function depends on where it's active. When released in the ventral tegmental area, it causes reward and happiness. In the basal ganglia, dopamine helps us coordinate movement.
Since I'm already on my soapbox, I'd like to point out there's more than 3 neurotransmitters. These are the basic ones:
https://en.wikipedia.org/wiki/Neurotransmitter?wprov=sfla1
I didn't know hormones and neurotransmitters overlapped like that; I always separated them in my head. TIL.
Why do I frequently see the neurotransmitters narrowed down to dopamine, norepinephrine, and serotonin? Are they the most important ones?
That's a surprising statement to me. Honestly, those aren't even the most important. Glutamate is the most common neurotransmitter in the brain. But dopamine, norepinephrine, and serotonin are responsible for some very "classic" bodily functions like reward, adrenaline, and sleep.
Now, hormones are typically separate from the brain - there's a barrier between neurons and your circulating blood maintained by astrocytes. This is the so-called blood-brain barrier. I do not know if there are examples of Oxytocin and Epinephrine crossing the BBB, as I did not study it. https://en.wikipedia.org/wiki/Blood%E2%80%93brain_barrier?wprov=sfla1