Piston stops pushing block after pushing some blocks

What I expected to happen was:
It should continue pushing blocks.

What actually happened was:
It stopped pushing blocks after 12 blocks.

Steps to Reproduce:
1-Make a redstone circuit that pushes 1 block in 1 tick. See 1st image for an example.
2-Put a block to push the block, see images for examples as I said.
3-After 12 blocks you notice that the circuit stops working.