I've noticed many times that most of the contract do not import directly from Open zeppelin (for example IERC20 Interface, Ownable Interface, Safemath library and so on) but rather the full code is imported inside the smart contract.
Look at the Shiba Inu Smart Contract: https://etherscan.io/address/0x95ad61b0a150d79219dcf64e1e6cc01f0b64c4ce#code
Inside the contract the IERC20 interface and Safemath library are copied rather then included from Open Zeppelin as an import statement.
Is there an advantage of doing so? Contract size advantage?