Because there are two kinds of crypto exchanges. Ones that have banking and can deal directly with government issued fiat currency and those that don't. If yo

Because there are two kinds of crypto exchanges. Ones that have banking and can deal directly with government issued fiat currency and those that don't. If you don't have that banking then your pairs are all in USDT. If the Tether/USDT scheme goes to hell those exchanges w/o banking lose out to a degree so I think it is in all their interest to cooperate.