Autotune was designed to correct pitch that was out of tune. It was used very subtly in older songs. But now it's a fad that people thinks sounds cool over any vocals. There's a possibility that it is trying to emulate the talk box effect popularized by Roger Troutman, but like you mentioned, it's a lazy way of going about it. I also think people without proper vocal training use it thinking it will automatically make them sound like they somewhat have vocals, but is often abused like the video above.