To use an example a little less generic/more detailed than my earlier remark; I actually had a friend who was a wonderful RPer, but he had nerve damage from his military service which left his hands stiff and with a tremor. It wasn't that he wanted to type like he did, but he often had extra spaces or transposed letters and it made his portion of a scene very hard to read, because if he typed very precisely it took him forever, and he didn't want everyone to wait on him.
He was on Windows and didn't have an option for autocorrect, but he remarked at one point when someone else complained about their autocorrect turning a thematic term into something else for the third time that, if he had the option, he would absolutely have had an automatic correction system on.
So, yes, it's actually very useful to some people. I personally find the autocorrect annoys me (both because, say, if I'm trying to use a term like 'volus' and it turns it into 'bolus', and for the aforementioned go/og -> of) and so I turn it off globally, but not everyone does. Some out there do find it legitimately very useful.
That's actually supposedly why Apple put autocorrect on the desktop. Not because it's like a phone, but primarily as an accessibility feature. (Having it on by default is the decision I might question, as no other accessibility features are. But regardless.)