It may not exactly be about artist. For instance person mixing the artist's song (putting together all the individual instrument and vocal tracks and ensuring i

It may not exactly be about artist. For instance person mixing the artist's song (putting together all the individual instrument and vocal tracks and ensuring it sounds good together) may use autotune without artist even knowing. Then you have problem of the budget. Studio time is quite expensive and after nth take hard decisions have to be made. Booking another session or fix the tuning with software? Also take into account that vocals that you hear in songs, that are not obviously autotuned may actually be composed of dozens of takes. That technique is called comping and the mixer (sometimes together with the artist) would choose the best take out of dozen often for each phrase or even single word. Sort of like natural autotune, when e.g. only phrases that sound in tune are picked.