You mean, instead of USD? Because most exchanges cannot and does not support withdrawals - they are virtual.
> Because most exchanges cannot and does not support withdrawals - they are virtual.
Can you elaborate? I'm not familiar with these exchanges, really curious. You mean exchanges accept cash for coins and don't allow withdrawals? :)
To allow deposit or withdrawal of fiat, exchanges tend to have to comply with international banking regulations, which requires a great deal of paperwork. As a result, only a few exchanges offer this - examples are Coinbase, Bitstamp, Bitfinex, Kraken.
Before Tether existed, you couldn't buy or sell dollars or Euros on a pure crypto exchange. That's a big limitation.
Among other things, Tether allows you to trade in USD on these crypto-only exchanges.
Basically, one problem Tethers solve is allowing exchanges to operate more completely without regulatory oversight. As such, the limitations in their transparency may be acceptable to many users, who know that they're not operating in a regulated market and are willing to accept some risk for doing that.