Why Put a Full-Size USB Port on a Smartphone?

In a widely linked-to post, Yanko Design featured a concept Sony-Ericsson smartphone by designer Vincent Palicki. The selling point of the design would be the full-size USB port that accepts flash drives and the like. To wit:
Crave Asia: "We actually would like to see this mobile phone with a full-size USB port on store shelves."
The Boy Genius Report: "This is about as far away from reality as any concept car you're likely to see in Detroit, but the prospect is intriguing."
Mobile Magazine: "Yes, this idea is very much a concept, so don't expect the final design to look like the picture provided, but it does provide intriguing possibilities."
Maybe there's a reason why Sony Ericsson hasn't implemented this "intriguing" concept. Instead of going through all that trouble of keeping a smartphone or PDA small while working in a full-size USB port, why not just use smaller versions (like the 4-pin USB port on gadgets like the RAZR)?
It's just a simple matter of bundling the right adapters, such as the one featured in the Belkin product pictured above, so that people can still connect their full-size USB peripherals.