Why did Wales join the UK?

Wales was never formally admitted into the Kingdom of Great Britain or its successor state, the United Kingdom, as an individual territory in its own right. Instead, beginning with the Laws in Wales Acts 1535–1542, the legal system and administration of England was extended to encompass Wales, effectively incorporating England and Wales into a "single realm known as England and Wales" (Wales and Berwick Act 1746). The Acts, including the most substantial Act of 1535, are sometimes known collectively as the Acts of Union between England and Wales, even though Wales retained certain distinct political arrangements until modern times.