And does it really make any difference? Probably not. But if they had decided to go with USB 3.0 that doesn't mean that they would have left eSATA out... they are not mutually exclusive technologies. It probably had more to do with cost as most controller chipsets have USB 2.0 and eSATA on the same chip. USB 3 has been on it's own separate controller.
Yeah, USB 2.0 and SATA are built into the Broadcom "system on a chip" processor. Definitely not worth adding cost to the box for USB 3.0.