Chips are great for 99.9% of the time, but the chip is never placed at the leading edge of the tire crossing the line. You still need numbers and cameras for that when it is really close. Until the winner of the race is defined as having the first chip to cross the line we will need the conventional things as well.
Having a number pinned on helps the officials with DQ'ing riders that are breaking rules. The official on the moto can't read your chip number.