Sometimes you need to blow compressed air to clear the channel being cut. Depending on the bit chips can sling out far and wide. I don't use the DC when I engrave or use a 1/8" end mill because there's just not enough dust and chips to put up with the noise of the DC. It's during those times I get to enjoy the quiet spindle with no hearing protection. But I used a 1.5" two-flute bottom-clearing bit the other day with no shield or DC at all and it flung chips 15' away!
To blow air and catch the chips you'd have to work with the air pressure/volume carefully so as to not blow so hard the DC can't suck it in but the idea has merit, Rick. I've worked up a couple of designs using that very combo but haven't built a model yet - one day, maybe.