It is good to add a require() statement that checks the return value of token transfers or to use something like OpenZeppelins safeTransfer/safeTransferFrom unless one is sure the given token reverts in case of a failure. Failure to do so will cause silent failures of transfers and affect token accounting in contract.
For example, Some tokens do not implement the ERC20 standard properly but are still accepted by most code that accepts ERC20 tokens. For example Tether (USDT)s transfer() and transferFrom() functions do not return booleans as the specification requires, and instead have no return value. When these sorts of tokens are cast to IERC20, their function signatures do not match and therefore the calls made, revert.
Consider using safeTransfer/safeTransferFrom or require() consistently.
