During the normal operation of GSA SER you don't need that, because you either verify old links or you post new content. In both cases it either works or it doesn't.
But if you import links bought on the market, or links built with other software together with account data, it's not clear whether the accounts can be used for further operations. The accounts might not be functional or GSA SER might not have an engine for them.
For that reason it would be great if GSA could try to login into them, either when importing them or through a separate operation, much like proxies can be tested or emails or API requests to 3rd party services.