The first glycolytic step yields glucose-6-P, that can either be degraded or stored as glycogen. The second step is reversible. Thus, this is the first compromising step in the glycolytic pathway. It's called the comitted step. Thus, it is highly appropriate for phosphofructokinase to be the primary control site in glycolysis.

High concentrations of AMP and ADP (produced by ATP cleavage) indicates low energy level in the cells. So, they must stimulate energy synthesis by exergonic pathways as glycolysis.