Why did the medieval town wanted to keep out the strangers?

Answer 1

1st Answer:

They didn't want to keep out strangers, but not many strangers showed up since travel was hard and most people didn't go beyond 5 miles from home.

2nd Answer:

People in medieval towns did not want to keep out strangers, but it was not because there were few of them. Quite the contrary, the single distinguishing thing that usually made a place a town, rather than a village, was the presence of a permanent market. In order for the market to thrive, there had to be constant traffic of trades people, people from the countryside, travellers, and so on. There was a fair amount of travel, because in addition to business reasons for it, people went on pilgrimages.