L2 is used as memory for processes where the answer is thrown away. Lets say the computer is trying to do 3 + 5 + 7. First, 3 + 5 is stored as 8 in either L1 or L2 then 7 is added to that stored number to get 15.
With no L2, the RAM would be used more and the computer would be slower than crap. So slow we might even call it 'Celeron'