I think once you get to a certain level you are too busy to deal with grammar. Management at my company is the absolute worst.
I think they think that's true, but they're wrong. Grammar is second nature. Switching back and forth from bad to good -- because no matter who you are there are times when you have to use good grammar -- is more trouble than simply internalizing it to begin with.
Sometimes when I have 10000 other things on my mind and I'm responding quickly on my phone it's easier to simply say "yeah sounds good - make sure to include this in press release next week too thanks taylor" than typing it out properly. But, I only do this when talking with my colleagues, not managers. If I was running a company, I have no managers and therefore would be able to do it all the time.