You know, people who lack the ability to connect with others may have a some emotional detachment issues.
That's right. Emotional detachment is the avoidance of emotional connections. That sounds like a lonely condition.
Very much so, as well as a means of coping with anxiety by avoiding certain situations that trigger it.
It can also be a reaction to a chronic condition such as depersonalization disorder. It is definitely a coping mechanism.
Traumatized people subconsciously mutes their emotions in order to protect themselves resulting in the socially withdrawn behaviors.
Depersonalization is a condition where people feel detached or disconnected from themself. I would hate to have that condition.
 There are many causes of emotional detachment disorder and it manifests differently for everyone. 
True. People have it to maintain a sense of boundaries and psychic integrity, as well as avoid undesired impact on others.
A lot of people don't stop to take it into consideration why some people don;t keep in touch and don;t ever gert out of the house. This is a great example of actions (or lack of) affect the individual as well as those around them.
I agree, it is a decision to avoid engaging emotional connections. It is also an inability to maintain the connections for personal and social reasons.