Once North America was settled, the king also received income from duties imposed on the raw materials (such as tobacco) shipped from Virginia to England. When more people immigrated to the colonies, more deershins, tobacco, lumber, and other products were shipped to England - and thus the more income the king received from import duties.
So it made sense for the king to grant title to colonial lands to others, especially if they would stimulate economic development in North America. The original charter to the Virginia Company had provided title (at least according to English law...) over a vast swath of the North American continent to a small group of venture capitalists in London. They were undercapitalized and could not make a profit from their investment, however, and in 1624 the king revoked their charter.
In 1632, King Charles I carved Maryland out of the lands defined as "Virginia" in the Third Charter. He gave the Calvert family proprietary rights in that colony, and in the process defined the edge of the Potomac River as the northern boundary of Virginia. In 1649, his son Charles II gave the Northern Neck (in what became known as the Fairfax Grant) to a consortium of allies during the English Civil War. In 1663, he created the proprietary colony of Carolina, rewarding other friends and establishing a new southern boundary for Virginia.
With these exceptions, however, other land grants were issued to individuals and to organizations from the king's officials in the colony. "Headrights" issued in the first century of the colony authorized an individual to claim 50 acres, and after 1745 groups of politically-connected individuals established land companies to speculate in unsettled lands. Between 1730 and 1745 in particular, large tracts of lands were granted to individuals who promised to increase settlement on the frontier.
The royal governors who issued land grants could use that authority to build allies among the Virginians and, by delaying approval of a survey or grant, to punish their enemies. Governor Spottswood rewarded himself by steering early settlement up the Rappahannock River rather than the James River, in part because he obtained rights to large tracts of land in the headwaters of the Rapidan River near modern-day Germanna.