Utility of two pins requiring same voltage
IC manufacturers use more than one pin on a device if the device is a high current device.  

As a LED driver, it's likely a high-current device and thus needs more than 1 pin to share the current load through the device. 

EDIT: 
After seeing the spreadsheet , it seems this particular device is not really very high power after all, at only 800mA total, so one further possibility is that the designers wanted to use the extra connections to power and ground to help dissipate heat from the chip to the PCB though the power leads.