Specifically, someone who has never experienced other places? A college professor once used the term "parochial" in this context. "You should earn your doctorate from another graduate college, then you will not be so parochial in your studies".
Provincial carries a connotation of not having left one's home town or province. It is a synonym to parochial not having left one's own parish.
I originally had inbred listed here. I believed the reasoning self-explanatory, but, it was causing too much confusion for people. I suggested this because of the example given of going elsewhere for further schooling.
Institutionally speaking, we describe programs where everyone was trained in the same place as being inbred. It is not usually applied to the individuals themselves. But, it can be applied to their ideas.
The terminology refers to the breeding of ideas without outside or fresh input. It is metaphorical to consanguinity where an isolated population can become inbred over generations of interbreeding.
Depending on whether it's AmE or BE, you're probably looking for
Meaning from Oxford Dictionaries:
NOUN (plural homebodies)
• informal , chiefly North American A person who likes to stay at home, especially one who is perceived as unadventurous: since his marriage, Brett has become a homebody
I think to answer your title question that person (in the most extreme sense) would be a shut-in.
Soemone who doesn't get out very much or leave their home, ususally due to illness, handicap, old age.
If you are looking for something to replace parochial attitudes, in AE we would use small-town attitude/outlook.
Given the context, it looks like the professor is saying that earning your doctorate at another college will make you more worldly. worldly means having a lot of practical experience and knowledge about life and the world. (ref). Synonyms of worldly include sophisticated, experienced, refined, and broad-minded
Appropriate antonyms might be unworldly and unrefined, but you can start picking your own from a thesaurus. Of course, an antonym of parochial is broad-minded, and your professor's word choice is accurate.
For someone who literally never leaves or never left their home, here are some terms that might fit your context:
cave-dweller: metaphoric, meaning someone who have not evolved to the point where they have left their cave.
hermit: A person who has withdrawn from society and lives a solitary existence; a recluse.
recluse: a person who lives in seclusion or apart from society.
None of these literally mean never left their home, but they imply a sense of isolation from the rest of the world.
Language would be boring without vivid imagery in words. Using words like these tends to encourage it.