ERC20 defines contract signature for contract in order for them to be accepted by wallets, exchanges etc.
I have seen that for some reason, even when signature contract (interface/abstract contract) is not reused, token contract inherits from contracts that has this signature. Typically those interfaces have name like ERC20.
I have hard time to understand why they do that. If my token contract is the only source of ERC20 signature, meaning, I'm not using any interface or other contract that token contract inherits form, will that mean I will still comply wallets and exchange networks? I do not know how third party applications manages that, but I think my contract should be valid.