An approach like that would be suitable for this case, but it doesn't and cannot scale to be suitable for the general, standard process that can work for blocking abusive accounts on Google scale. All kinds of spammers, trolls and simply abusive users are able to create many accounts (often in a semi-automated way) and create new ones when you block them. You need a way to block hundreds of thousands of such accounts every day in a cost-efficient manner, because the service is free and revenue per user - low. This applies to pretty much any free service with a large user base, by the way - all of those need ways to efficiently ban lots of accounts and can't afford to negotiate with the banned ones.
This means that you pretty much need a way where the average time spent per blocking an account (including any answers and appeals if you allow them) is measured in seconds, not minutes; and the accounts that need to be blocked will use these facilities just as much, and likely more.
In addition, you generally can't simply give a straight answer in public (the only reason why they'd want to give a straight answer, due to this publicity) - reasons for blocking accounts involve either claiming that the account owner has done something shady, or involve non-public data (e.g. if child porn was transferred in emails or something like that). If you want to publish specific claims of abuse performed by someone, you need to be very thorough and careful about anything you claim (much more thorough than you want to be when choosing to block accounts - you need to be able to block accounts quickly and efficiently) or you open yourself up to all kinds of libel issues, so that can't be done as a routine customer service activity without involving lawyers, making the process even more expensive.
This means that you pretty much need a way where the average time spent per blocking an account (including any answers and appeals if you allow them) is measured in seconds, not minutes; and the accounts that need to be blocked will use these facilities just as much, and likely more.
In addition, you generally can't simply give a straight answer in public (the only reason why they'd want to give a straight answer, due to this publicity) - reasons for blocking accounts involve either claiming that the account owner has done something shady, or involve non-public data (e.g. if child porn was transferred in emails or something like that). If you want to publish specific claims of abuse performed by someone, you need to be very thorough and careful about anything you claim (much more thorough than you want to be when choosing to block accounts - you need to be able to block accounts quickly and efficiently) or you open yourself up to all kinds of libel issues, so that can't be done as a routine customer service activity without involving lawyers, making the process even more expensive.