I sense you think this is a bad thing... Are cars made by hand any more? Does being made by robots make a car any less fantastic?
The difference though is that a car is a physical object produced by a persons talent. A vocal track is (in spirit at least) something produced directly, or a direct output of the vocalist. Part of the mystique is supposed to be the fact that not everyone can carry a perfect tune. Except than when you apply too much technology post-processing, you eliminate the exclusivity (and garbage up the track at the same time).
I just think it's strange to apply inconsistent standards to the same genre. It's ok that the music is precision-engineered on a computer, but not the vocals? Have it one way or the other.
http://en.wikipedia.org/wiki/Vocaloid
I said 'sort of' because the entry said "with specially recorded vocals of voice actors". It isn't completely synthesized.
Then came Auto-Tune. That meant that less perfect singers no longer would have to strain themselves by performing a dozen tracks, we could do with three or four, focusing on performance and feel. AT would assist with the pitch. Sessions actually became more creative, since the tools were better than before.
So "perfect vocals" have been around way longer than Auto-Tune. We just did it in a more tedious way, and wore out the singers vocal cords in the process. Pop is just pop. Other genres will always cater for those who want to listen to more "real music".