Everyone's got a spell checker. Ever proof a document and it has these kinds of errors?
"Please leave the key in the sync and don't share there lock code in pubic."
Yeah, you have to be careful what you do in pubic. A spellchecker is not going to catch everything. And most grammar checks suck. No qualification needed. Suck is correct. I use Grammarly. CLEARLY not for everything. Informal righting is no problem. Yeah, that was intentional. But if I'm going to hand someone a contract to sign, things could get a little ugly if I do the grammatical equivalent of a decimal point in the wrong place. "There airs" and their heirs might put us before a judge.
Grammarly rides along with email, documents, websites, and prompts me when I've blown it (on the fly), and also conducts a final check, if (and only if) I ask it to. It's also FAR more robust than the built-in grammar and spelling check in Google Docs or Word. Seriously, if I can stump those tools just by talking the way I talk, I'd better have a tool I can't break. Since one contract can make or break a deal, I figure the $12 or so a month is worth it. Yeah, that's all it is. Cheaper if you have people working for you, which brings up a delicate point.
To HELL with delicate! You've got people working for you or WITH you who can't write to save their lives. And they can make you look like ASS. Guess what you're getting for Christmas, Roger? That's right. I got you a year of Grammarly—now freaking turn it on, because I put a lot of thought into this and wanted to get you a TOOL that you'd USE. I know, Roger. I know. You can spell good. After ten years since High School, there's no way you've let your grammer fade into Bolivian.
Grammarly is how to tell someone you love they're sorry—in a nice way. You can sign up and install Grammarly faster than Roger can look up "malapropism". As far as tools go, it's the Swiss Army knife of keeping your writing intelligible without the corkscrew of crap that no one uses.