People who earned a certain amount of wages were required to own longbows. During Henry II's reign, people who earned between two to five pounds a year had to own bows. Such laws were instigated for the average citizen and not the military, as they might be called upon to serve the king. Citizens who earned enough could also be required to carry a bow whenever traveling.
Churches were always required to keep targets on their premises so that anyone who wished to could go there and practice with their longbow. People were expected to become proficient and were required to stand a good distance from the targets to become accurate with their aim.
Sunday was the mandatory day for English citizens to practice their archery abilities with their longbows. Since churches were required to always have targets present there, it was convenient to practice on the same day that services were held.
These laws promoted regular use of the longbow and therefore an increase in skill in the general citizen when using it. At the time any professional soldiers were mercenaries and not part of a standing army. Having armed citizens to aid in a fight was practical. Medieval times required these types of laws to protect the kingdoms and the people from outside threats.