I was going through some of my notes today and noticed they contain quite a lot of typos. While autocorrect might help at some situations often it's not even recognizing the word or offers a completely wrong word.
While the autocorrect might not understand all my mistakes it's often easy to me to know what word did I intented to write, even after a long time. But today I found a word I wasn't sure what I had written. It could have been just a spelling mistake, but it could have been a word that I wasn't familiar with.
While neither me or the spell checker didn't recognize the word Google did. Trying to search for it (assuming it was just a word I wasn't familiar with) Google actually gave the "did you mean" suggestion which actually made sense.
Of course there are computational limitations with the on device spell checker. But still, it took Google a fraction of a second to look that word up and determine the most obvious alternative where the Android autocorrect failed to suggest anything.