A previous employer, a freight broker with three employees, once composed a letter to send out to many of our customers and vendors regarding changes to our procedures related to billing and payments. He gave his final draft of the letter to the secretary to make copies and send out to those customers and vendors. After he left for the day, she gave me the letter, and asked me to read it. I came to the same conclusion as she had come to, that the terrible grammar, punctuation and spelling was nowhere near the level that a corporation, albeit a small one, should send out as business correspondence. The letter could very well be regarded as a negative representation of our competence.
The next day, we confronted the boss, and in as tactful way as possible told him that we thought a rewrite to correct all the bad punctuation, misspellings, bad grammar and run-on sentences would go a long way to maintain our professional image. Though initially somewhat offended, he relented and we all sat at a computer and rewrote the letter, turning it into a much more professional looking document.
I grew up in the 50s and 60s and went to a smallish rural school, but was relentlessly drilled on writing skills, which have served me well in life. It's good the have those skills, my daughter was a school teacher and I wouldn't want to send poorly composed emails text messages to her.