In the medieval times Why did villages spend all of their lives in the same village?

Travel was by foot for the residents of a village. The Lord of the Manor would be the only one with access to horses. Some of the villagers and local farmers would travel to neighbhouring villages on market days for trade, but travel generally was limited. This is how local accents came about in places like the UK. Each village had their own form of the language because of the isolation.