That's part of it. The chicken you get from a store is almost certainly a Cornish Cross, which reaches market weight in something like 5 weeks for a fryer and 8 weeks for a broiler. Heritage breeds (read: "real" chickens) take 20-22 weeks to reach maturity. The meat is very, very different -- dark meat is *dark*, far more flavorful, and requires more time / different methods to cook since the muscles have actually been used. CC's mostly do two things: eat and shit. They really don't move around a whole lot.
Anyway, CC's don't really forage a whole lot anyway, so even if they're raised in a manner that they can eat grass, bugs, etc. they usually don't -- they plop down in front of a feeder and just gorge. They're *amazing* birds, but their quality of life is horrible. It's impossible to beat them on feed conversion ratio, though, which is why that's pretty much all you see. There are some other breeds making their way into the market that take 3-4 more weeks to reach maturity but they're still very, very much in the minority.
Stellar rays prove fibbing never pays. Embezzlement is another matter.