I noticed that the total trading amount of DAI per day on Binance and OKex is very very small. Will there be a problem of low liquidity if I hold DAI?
Of course it is. DAI is not as popular as the aformentioned centralized stablecoins (USDC and USDT). You should expect low liquidity for DAI just because it's decentralized. If I'm not mistaken, you can find more liquidity in Uniswap. It's a DEX where you can swap DAI to any ERC-20 token living on the ETH blockchain.
Despite DAI's limitations, it's still a better choice than both USDC and USDT. There's no censorship of any kind. You and only you control access to your funds. The only risk would be DAI losing the USD peg once ETH and other crypto coins go all the way down the drain. After all, DAI is a collaterized stablecoin. If Maker (the issuer of DAI) has an emergency plan to protect DAI's USD peg, there should be nothing to be concerned about. With or without stablecoins, crypto will be here to stay for a long time.
