Because machines don't care what you do, or who you are. Humans potentially do. They can gossip about you, they can read, and understand, all your private emails and use that information against you.
Humans are slow. Gmail's computers are programmed to wring the most possible profit out of millions and millions of accounts. Seriously, I'm convinced the humans would do less damage.
I'm convinced of the opposite: humans judge basing on incomplete and incorrect data, they are often malicious and selfish and blinded by personal gain.
Computers don't have prejudices, don't have a motive, and work on the specific task without being sidetracked by feelings.
Computers follow instructions of the programmers. If the programmer is good, the computer has the same prejudices. Specifically, if the programmer wants to find juicy gossip, a computer lets her do it faster. If the programmer respects users' privacy, so will the computer. (If she's not good, the computer has random prejudices. https://en.wikipedia.org/wiki/Hacker_koan#Uncarved_block)
1) If the programmer is good the computer COULD show prejudices. It's not an implication. I can be a racist bigot, but if I'm a good programmer I will not prevent login for the users 晴輝, Abd al-Aziz or 湘. I can build a watermill and it will not have prejudice, it will just do a job.
2) The programs running in such big companies are peer reviewed, so the inner workings are known and checked by at least two people. You cannot do that to human beings. You don't know what they are ultimately trying to do AND you cannot have at least two people checking on them. If now you're thinking of parents, remember that they have a limited influence on a person.
3) Random prejudice could still work, just like random noise, but I still disagree on the prejudice part.
> I can be a racist bigot, but if I'm a good programmer I will not prevent login for the users 晴輝, Abd al-Aziz or 湘.
However, if you were a programmer with a very insular mindset, you could create a system without support for such non English names, by not even considering that non English users would use the service. Just an example of a prejudice that could show though.
