The early European ocean voyages of the Age of Discovery did not always lead to the discovery of unknown lands. Their main objective was to obtain as much profit as could be made. Exploration of new coasts, with the associated benefits for science, was a secondary consideration, performed only to the degree necessary to bring success to the economic purpose of the voyage.
The early Portuguese and Spanish sea captains were true explorers, in the sense that their contract with the crown (four fifth of the profit to the explorer, one fifth to the crown) was based on voyages to unknown destinations and therefore carried great risk. The British crown found it more profitable to raid the Spanish outposts in regions already discovered. It financed Francis Drake, Thomas Cavendish and other "privateers" to sack Spanish settlements and capture Spain's ships.
The profitability of marauding voyages was beyond doubt. When Drake captured a Spanish galleon in 1579 he obtained 13 chests of silver coin, 26 tons of silver bullion, 80 pounds of gold, and uncounted jewellery. Cavendish sacked Puna Island off Peru, slaughtering its Indian inhabitants, in 1587; he returned from his two year marauding voyage with a booty worth 125,000 pounds, nearly half of the Crown's annual revenue. Such adventurism did not contribute much to science.