Say there is a circuit with two 1.5V cells, and a 100 ohm resistor.
If you connect two cells in series, then the total emf is 3V. And the current will be 3/100 = 0.03 A. (Using V = IR):
If you have the cells in parallel, then the total emf is 1.5V, as the terminals of the cells are electrically the same point. So the current will only be 0.015 A:
But if you just had one 1.5V cell, so the total emf is again 1.5V. The current will still be 0.015 A.
So what benefit does adding a second cell have? The emf and the current is the same no matter if you use 2 cells in parallel or just one cell.
I'm assuming that all the cells are identical, and internal resistance is negligible.