Fly a jet into CTAFs porter?
When youre above the light aircraft and and with less than flaps 2 in a jet, they can be very tricky to spot blending with terrain below you. Not to mention the workload still in the flight deck. It's not until you're fully configured with a stable FPA and forward vision, plus the major workload complete that you can see the little buggers. This usually coincides with turning final or less than 5nm from touchdown.
Plus quite often the lighties are transiting coastal outside of the aerodrome vicinity, but within conflict of a jet on approach. They are VFR and are not on frequency.