Is there a reason for IERC721Receiver.sol, and why shouldn't I just do this?

Support Contracts
1

Hello, I've been trying to implement IERC721Receiver.sol and it seems like I can't really find a reason why we need to have it, or import it at all.

The following code(s) return successful for _safeMint function on ERC721 contract.

    function onERC721Received( address operator, address from, uint256 tokenId, bytes calldata data ) public pure returns (bytes4) {
        return 0x150b7a02;
    }

    function onERC721Received( address operator, address from, uint256 tokenId, bytes calldata data ) public pure returns (bytes4) {
        return this.onERC721Received.selector;
    }

contract x is IERC721Receiver {
    function onERC721Received( address operator, address from, uint256 tokenId, bytes calldata data ) public override returns (bytes4) {
        return this.onERC721Received.selector;
    }
}

heck, if it wasn't for the caller function in ERC721.sol, even this would work!

function onERC721Received() public pure returns (bytes4) { return 0x150b7a02; }

why do we have to go through all the hassle of importing this contract, inheriting it, and then adding a function that does not even use the variables besides to accept it from the erc721 contract, when in reality the whole point is just to return a FIXED value?

2

essentially isnt the solution the same if _safeMint just does something like this?

if (to.isContract()) {
try IERC721Receiver(to).onERC721Received() returns (uint retval) {
return retval == 1 
}

then contracts can just add a simple

function onERC721Received() public pure returns (uint) { return 1; }

to achieve the SAME result?