Why some areas of our body don't own receptors for discomfort?

Why some areas of our body don't own receptors for discomfort?
pain evolved as a protective appliance. when you sense pain, you cancel from the painful stimulus to prevent further injury. from an evolutionary standpoint, human being able to sense agony in the brain for instance probably didn't contribute any additional help to sensing pain just in the scalp or skull.
brain, heaps internal organs
The brain, the liver, most of the large intestine (the train has them), and surely others.
Parietal portion of pleura,peritoneum,and pericardium are devoid of pain fortitude endings . The root is not known.
coz in that is no need for them within those places...what can u do if u feel discomfort from a stroke or a heart attack?..can u re-open the arteries by ur self?