Time and cost. The chiller will never be as cheap as bags of ice, even over many batches. And while 22 minutes isn't a long cool time, there still is setup, sanitation, and storage to account for.
I hesitate to recommend this practice to some specific group. I think anyone can do this and benefit, and I'm glad to hear it's worked for others. I will say, that I think there's tremendous value for the new brewer who hasn't invested in a lot of gear (for whatever reason).
Also - There are a ton of threads out there where guys say they've started brewing to save money on beer. In all of those threads, members jump in to say it's not true and that they'll ultimately wind up spending more. There's no reason for that to be the case. Homebrew costs me $0.25 to $0.75 per bottle. One important way I accomplish that is by not splurging on equipment like a nice chiller.
I brew like once a month. Sometimes more. Someone brewing several times a month could reasonably make up the cost of a chiller (and other equipment). The casual brewer won't.