P/S piping lets several circulators of different pumping ability "co-exist" within the same system without interfering with each other. In effect, the closely spaced tees allow each circuit to be thought of as a standalone circuit, not connected to the other circuits. You might even say that a circulator in a given circuit of a P/S system "doesn't know the other circulators and piping circuits even exist." This isolating effect makes it relatively easy to design sophisticated multi-load systems without concern over how flow rates and pressure drops will change as various circulators turn on and off.
The widespread acceptance of P/S piping has created market demand for new products that implement the concept while also speeding the installation. Several such products have appeared in the North American market over the last couple of years to address this demand. When properly applied, they can improve performance and lower installation cost relative to traditional ways of implementing P/S design.