Traditionally, CubeSats were considered low-priority and risky, and so were ejected last from the rocket as a safety precaution. This severely limited the orbits available to CubeSats. However, the thinking vis-à-vis CubeSats is now changing, as rockets are now willing to “drop off” CubeSats at low orbits before the primary payload is released. Why? Because carrying just 3 P-POD deployers (9 1U CubeSats) is worth $0.5M to the launch company. It’s good business for them.
Also, the fully enclosed P-POD has proven itself to isolate the primary payload(s) from any bad behavior (early turn-on, parts falling off) of the low-cost, low-priority CubeSats inside.