Among the shortcomings, I would probably note the small number of supported networks. It would not be superfluous to have TRC20, it seems to me that USDT TRC20 is used by a much larger number of users than ERC20, for those who make frequent exchanges will pay attention to fees.
Here is the answer you are looking for, from the representative
We don't exchange some popular crypto assets because they represent considerable risks to us. We don't plan to support the Tron network for now, however we may reconsider it the future.
Users who want to buy risky/popular assets usually buy ETH from us then swap to whatever they like on liquidity pools (i.e. Uniswap).