I think its an interesting question, if not a valid observation.Mazda says that their decision to forego the 2 for the US market was made from cheap gasoline and tight supply from their Salamanca, Mexico facility. Senior VP of US Ops Robert Davis laid it out to Autonews. "We could have had it, but we would have had a number that didn't make much sense with 600 dealers and with the marketing it takes to launch a new car," he said. "I wanted to allocate resources to those products that make us and our dealers considerably more profit than a Mazda2 does."
Now no one is quite sure how many Scion dealers exist outside of Toyota, but the consensus seems to be around 1,000 of Toyotas 1,225 US dealers. So Mazda doesn't see enough supply to service 600 dealers, yet Toyota is comfortable servicing ~1,000?
In 2014 Mazda sold 13,615 Mazda 2's, roughly 24% of Scions total volume last year. IF Scion is to move near that number of iA's (which I see entirely possible, they moved ~16K xB's, ~18K tC's, ~14K FR-S' in 2014) They're looking at moving ~14 cars per dealer.
Now the secret may lie in fuel prices. Mazda passed on the new 2 because of lower fuel costs. The Mazda 2 rode the wave of high pump prices to modest success over the last 4 years. BUT Scion has the advantage of being viewed as a value brand. While shoppers may of piled into the Mazda 2 because they were running from their fuel bill, Scion doesn't suffer as badly from the elasticity of fuel costs as badly as Mazda does, in my opinion that is.
While Mazda may not have faith, Scion has plenty of hope their new runabout will prosper regardless of prices at the pump. Now the question is, can Mazda supply them with enough cars?