Why BEx query not hitting aggregates?

Hi

I already read lots of documents regarding creating aggregate.

I try following procedures to create aggregates on cube:

1) Create separate aggregate for each dimension.

2) Create separate aggregate for each dimension with time dimension.

3) Single aggregate contains all dimension.

4) System proposed all aggregates.

5) Selected optimize aggregates from system proposed all aggregates.

Non of the aggregate size is greater then InfoCube size.

Following are the best valuation when using option (2):

But

Why BEx query not hitting aggregates?

Thanks