I think you're right in that they wanted to provide a wider gear range than the IGH would provide on it's own, - maybe just to make it look good on paper.

This bike and the Breezer however, are different beasts. The Breezer is supposed to be a performance commuter. It has an extra long top tube to stretch the rider into a more aero position. They custom designed the rear rack to save weight. It looks to me like Breezer is targeting those folks who want to go fast but don't like drop bars. The relatively low gearing seemed inconsistent with the bike's niche and I'm guessing they just decided to live with it.

This Schwinn looks more like a typical hybrid/upright bike and would be fine without a front derailleur. Like the others have said, having a front derailleur detracts from the advantages of having an IGH. This bike might be an exception to the rule: "The whole is greater than the sum of its parts".