The question is rather: why use Mercatox when there are at least another 30 better, larger, liquid and safe exchanges.
In it only 10 coins around make 100k $ of volume per day .... everything else is impossible to exchange, because maybe with $ 5000 you get up the price of 100%
In addition, the "minor coins" wallets are almost always maintained or not synchronized.
I do not think it is Scam but I strongly discourage its use, as well as exchange Yobit!
First rule to earn money:
do not lose money!