xpub keys are BIP32 extended keys. Armory does not support BIP32 yet and thus does not produce these keys.
Well Armory development has stagnated recently due to ATI having issues and no longer developing armory. Goatpig is the only active developer now and he it's planning on adding BIP32 support as well as other improvements to make up for the technological gap that armory suffers.
Thanks for the info. Wow isn't bip32 from 2012/2013?