You deposit 400 UNI and get $50 in free credits for trading - just did it and will be getting the credits next week.
What if Huobi suddenly cease trading and close all accounts and exit scam? You will then be left from 400 uni that is worth over $2000 and also without $50 token that the y gave you. Point of cryptocurrency is decentralised finance. Now keeping your coins on centralised points of failure.