[0xcde4c3db]

My WAG (all points are conjecture):

1) There's only one SATA port on the southbridge.

2) USB-SATA chips are cheaper than SATA port multiplier chips.

3) They needed a USB hub anyway for other stuff.

[rasz_pl]

Those Marvel SoCs are build on NAS oriented IP, they have tons of SATA ports onboard.