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