I think this is a mindset thing...while light and "tossable" may be true to some degree, it's still no handling champion. Folks want cheap transport, and this is what you get - a really amazing offering compared to what used to be "loaded" 5-10 years ago (hell, my 2010 Mazda3 still doesn't have Traction Control...the Yaris tested did, along with a screen!!).
...but you have to compare the iA to the Corolla beside it (or the closer-styled Mazda3?). Pricing-wise, they're within an earshot, yet you get so much more of a substantial car with the compact over the sub-compact.
In 2010, we went to the Toyota dealership to buy a Yaris, but ended up with the Corolla - it was $500 more, yet offered so, so much more.
I love the Fiesta for a lot of reasons, but I'd never buy one when the Focus is sitting beside it for about the same money.
-ST trims, on the other hand...the Fiesta seems to wear it for a LOT cheaper. Unless the savings are substantial, there's not much better about subcompacts.