according to me .. USD is a strong currency and a stable measure for other currencies. USD can also be accepted throughout the country because it is the exchange rate that is international. why do people compare with bitcoin? may depend on each person .. if i compare bitcoin with local currency .. so i know clearly. when I get the advantage or disadvantage of bitcoin .. because comparison sepeeti it is important in gain bitcoin advantage. I always see the movement of bitcoin against local currency and USD because we will know the price direction of bitcoin.