Obviously, because there was gold there and they wanted some of it. This was augmented by the fad like nature of the Gold Rush. Many people were attracted by the "everyone is doing it" aspect.
While a few people got rich by finding gold, but more people got rich by selling supplies to the ones looking for it.
The thought of getting rich did attract many, but another big reason was the chance for freedom. California wasn't yet a state and laws weren't particularly enforced. There was no established society except for those of the Native Americans, so people could basically create their own.
The discovery of gold in California in 1849 attracted thousands of settlers seeking to make their fortune by finding gold.
300,000 people migrated to California for the gold rush.
many people mover to a part of California that gold was found
300,000 men, women and children came to California for gold
Wealth and power in a time when that was scarce.
The gold Rush had attracted many people to migrate and to come to California in 1848 and 1849. THE GOLD RUSH
It was important because many people really wanted money so many people hurried over to California hoping for the least bit of gold.