Ask HN: Why does the default MS spellchecker treat some language nuances as bad?

I've noticed that the default settings on the MS spell checker will be triggered on some common phrases, and suggest a more direct approach to describing stuff. What is the reason behind this? Do people find it valuable to get suggestions about replacing "at all times" with "always", and so on? Sometimes it will react to nuances that were intentional, and replacement phrases that were written to avoid a repetitive expression style.

What's the reason behind all this?