There aren't OCP's who know everything. There aren't PEOPLE who know everything.
Frankly, sometimes I need to do some tasks that are covered by OCP and still need to check documentation. It's hard to remember exactly the steps when it's not a routine task, but at least the OCP program provided me the knowledge to know the WAY to follow. In-depth information can always be gathered on Metalink and official documentation.
About getting OCP for a good job, well... it's better than nothing, but a certification alone won't bring many benefits. Experience is still the difference.
An ounce of action is worth a ton of theory.
—Friedrich Engels