Bitrex and polo don't have millions of dollars in people's money in hostage. Cryptopia does.
They also have - there simply users block accounts for withdrawal, which by the way sufficient number of BTC, and millions of dollars on one, and this happens (Bitrex).
There are simply volumes 100 times smaller than on the Bitrix, and the problems are not with user accounts, but simply a large-scale problem with many coins (there is no confirmation and synchronization of the purses of accounts with the blockchaine)
I SCAM
YOU SCAM
THEY SCAM
ALL SCAM
sometimes, often or rarely, covertly or brazenly
Cryptopia, Bitrex, POLO HiBTC EXMO YOBIT Binance /............................................................................................

