Bonus for opening new account

Various US banks have $300-$450 bonus offers just for opening an account with them and direct depositing $2,000 within 90 days.

What stops you from opening an account with one bank, and after receiving the bonus closing the account and doing the same thing at another bank? Is this a hack for some free money or is there a catch?

With my salary I could do one bank a month and wouldn’t be mad about having the extra cash.