Folks old enough should remember Disney was a premium cable service like HBO back in the 90s. Now its part of the standard cable package. Them starting their own streaming service makes sense. Any kid starting at the age of ~4 knows how to go to Netflix and find cartoons, etc and their mom's are always asking why the old Disney animation is not streaming anywhere. Disney streaming will have no issues succeeding quickly.
Not sure about the ESPN streaming app though. Their contracts with NFL and ESPN probably have to be modified which is why they are not included yet. But I'm not sure why folks that want live sports wouldn't just go back to cable or keep using their parents login. I went back to FiOS cable this week. I've been using PS VUE but they are increasing their cheapest tv service to $45 a month so it didn't make sense to keep it anymore. FiOS got small tv packages now that they are throwing in with their internet service. I got the sports/news (ESPN/NBA/NFL/CNN/ etc) package with the gigabit internet service for less than what I was paying for internet/PS VUE.