[EGreg]

I have always wondered why spelling and grammar checkers - which could easily fit on your computer back in the 90s - needed a cloud-based provider.

One could easily build chrome extensions that DIDN'T phone home.

Today deep learning data can be downloaded to each computer. They are doing it with small IOT!!

[vbezhenar]

Because their algorithms are their valuable intellectual property and hiding them behind server is the only real way to protect. Of course it has nothing to do with performance.

May be they use some statistics over uploaded texts to improve algorithms.