Lets take PM posts as an example. Why do we have a preview button?

I preview every post I make here at least 3 and sometimes a dozen times--perhaps it is possible for the gods here at PM to confirm this? For the last year, I have had installed and use a spell checker integrated into my browser specifically for this purpose.

And I invariably go back to each of my posts a few hours or days later and I nearly always find further things to correct. Doubled words, or missing words, or homonyms, without even considering obvious grammatical errors. Things I simply do not "see" the first few times.

There is no lack of care or laziness involved, but still I make these mistakes. Look further.