He means they don't support withdrawals of fiat currencies like USD or EUR. Many crypto exchanges only support withdrawal of crypto currencies.
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.
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.