Why is it that nobody’s marketing broccoli and bananas? This stuff is sold in stores, in exchange for money. Presumably there are for-profit enterprises out there with a vested interest in selling more.In contrast to candy bars and potato chips, most fruits and vegetables have no packaging and thus no easily identifiable brand name. An ad for Bob's Broccoli will probably help Betty's Broccoli sales since it's not clear which is which. Advertising for healthy foods becomes a public good and, thus, under-provided. Note that some vegetables do advertise--Express Salad Mixes keep popping up--but these vegetables have packaging.
Couldn't all fruits and vegetables have packaging? In theory, sure, but such foods spoil more easily (they are often sprayed with water to keep them crisp, something packaging would prevent). Note that Express salad mix is a mix, not just a head of lettuce in bag so there's good reason to give up a bit of freshness for the convenience (their ads also underline how fresh their mix is). Many customers like to investigate such foods before buying them. If you package your food, that makes it harder to inspect and customers might think you're hiding something.
So why don't we see ads brought to us by broccoli farmers? I've seen ads for why natural gas is so great and high fructose corn syrup isn't as bad as we think it is. Surely there's a national association of broccoli growers out there to wanting to get people off the sugar stuff.
And there is (unfortunately I couldn't embed the video).