[thebricksta]

Most superstar pop singers have fantastic singing voices and great pitch control. Autotune shows up because of some mix of 1) the modern pop aesthetic demands superhuman tuning, 2) some degree of autotune artifacts are expected as part of the modern sound, and 3) it can intentionally be used as an effect (T-Pain).

To give some more detail about both 1 and 2 -

Pitch control is more than just hitting the note; its about how well you can onset at the right pitch, how well you can hold the pitch once hit, how well you can jump each pitch interval and land on the right pitch, how well you can pitch through different articulations, different vocal ranges, etc. The modern pop sound has accepted that superhuman levels of pitch control that lock the vocal into tune with the perfectly tuned synthesizers/samplers are more important than a natural sound.

Also, since we've been using autotune for so long, it has almost become natural. We expect to hear it to some degree on every track, especially in more difficult vocal areas. If it wasn't present, one might feel the song sounds "indie" or worse, dated.

Lastly, one thing that fascinates me about the autotune complaints are that it's just one stage of a very long vocal processing chain. To my ears, the tweaks provided by dynamics processors are much more dramatic than autotune when applied to a reasonably proficient singer. Autotune is just one step of a processing chain that can easily run through 10+ processors to end up at the right sound.