people are used to $1.99 and the difference is that 1btc is one million ( 1 xbt = 100 satoshi) or 100 millions ( 1 satoshi) , the first looks better and its easier to switch to.
Besides we need new name (preferably ISO one) and satoshi would need to be shortened anyway.
there is another reason, 100 satoshi = 1 XBT even more reduces amount of zeroes needed to display value if its more than 100 satoshi and rounded. 100 XBT or 10 000 satoshi or 0.00010000 BTC
currently its really easy to get confused or make mistake especially by newcomers when you see
0.00010010 BTC or 0.00101001 BTC
I just realized that XBT you are asking is the same as µBTC which we already have on Peerbet (1 µBTC = 0.000001 BTC = 100 Satoshi).
its the same but XBT is easier to type than micro, and like i said we need ISO name anyway that's why some of us are trying to convince people to start using something simple for all to make adoption of bitcoin easier. Also when you are using 50 µBTC or 50 mBTC there is still chance to make mistake because its only one letter difference.