Answer:
There are many reasons why.
For one, the settlers were often ill-prepared for the hard word that the colonization process required. Many of them were not good farmers, and did not know how to grow food appropriately in the areas that they settled.
A second reason is that they often had conflicts with the Native Americans. The settlers believed that they could have more cordial relations with the Natives, but this was often not the case.
Finally, a third reason is that the first colonies started at a time when the Virginia region was going through a drought, which made things even more difficult for the colonists.