I completely agree that an outside scan is 100% necessary, but I also understand that no matter how good the pilot or crew, we will have lapses in our scanning. If you believe that your crew is perfect every flight, your mistaken. Having some sort of onboard traffic advisory has its merits, but it must be used as a supplement along with the eye ball. I have traffic being pumped directly in to the cockpit of my plane, and I certainly scan that display, but I use it as a quick reference, I don't stare at it. I then use its display to correlate traffic outside, and build that mental picture
. I understand that my crew and I are fallible, and we do our best, but I show up to the game with the understanding that we may never be perfect, even though we try. Please use all available resources, technology, and old school airmanship to be as safe as possible. Report accurate position information, only change flight path after clearing, and if you know traffic exists, put lateral or vertical separation between you and the threat.
Mike