I had a business acquaintance get her feelings hurt because I didn't follow her back when she followed me on Twitter. I looked at her feed and she literally had tweeted about her breakfast that morning.
I quit Twitter instead so that I wouldn't have to hurt anyone's feelings anymore.
I wasn't getting much value out of Twitter anyway (not a judgement on Twitter's value, just on what I was getting out of it), and my business depends a lot on maintaining healthy relationships with lots of people, since we grow primarily by referral. It just made sense to drop Twitter altogether and tell people instead that I don't use it.
I quit Twitter instead so that I wouldn't have to hurt anyone's feelings anymore.