Does anyone know why Queen Elizabeth I kept Northern California a secret?

In 1579, Sir Francis Drake landed 50 miles north of present day San Francisco and claimed Northern California in the name of Queen Elizabeth i. He named it New Albion. When he returned to England, Queen Elizabeth i made all the crew of the Golden Hind swear upon penalty of death not to mention New Albion, had the wrong latitude and longitude recorded in the ship's logs, and never published a map of New Albion. She kept it a secret until her death. King James later published the maps shortly after her death. Even the true location of Drake's landing was disputed until this century. Why keep it a secret? Wouldn't it have made good bragging rights to flaunt the fact that England had claimed land on two sides of a continent? The only reason I can think is she wanted to make Portus Albion (now Drake's Bay) a hidden way station for ships plundering the Spanish on the West Coast so they could dock and repair and evade the Spanish. Better guesses? I'm curious because I live near Drake's Bay.