Actually black people can be quite the good workers. When it comes to slavery laziness is of little consequence because if you don't work you are beaten and whipped. If you still refuse you are killed, which is motivation to all the other slaves.
As I said, today black people can be quite the hard workers. It would appear that your view of the race has been poisoned by rap culture, if you can call it culture that is. And of course you cant accurately generalize and entire race.