Why is the welsh flag not in the union jack flag?

The Welsh flag, featuring a red dragon on a green and white field, is not included in the Union Jack because the flag was designed before Wales was officially recognized as a distinct nation within the United Kingdom. The Union Jack, which combines the crosses of St. George (England) and St. Andrew (Scotland), was created in 1606 and later modified in 1801 to include St. Patrick's cross for Ireland. At that time, Wales was considered part of the Kingdom of England. Consequently, the Welsh flag has remained separate and is recognized as a symbol of Welsh identity.