Well yes. But Netflix was also one of the only streaming services in 2014 when the deal for these shows was made along with Hulu and an early version of Prime Video I think. But Netflix was the most dominant. It had everything in one place still at that time, so it was seen as better than the others.
The point is though, Netflix isn't the only streaming giant around anymore and as i've said time and time again, in European countries and even Canada, they have a plethora of TV-MA/R content on Disney+ via the Star brand, so these will fit right in. What these are doing in the US is acting as an excuse to open up the content range to TV-MA in the US.
Could we see a Daredevil Season 4? Possibly. But more importantly, this opens the door for them to add any TV-MA series or R rated movies to the service that they want. And again, as long as parents are using the parental controls correctly, they con't be able to access any of this stuff from their account, nor will they even be able to get into a parents account that is unlocked to TV-MA without a passcode.
I get all that but there's still something weird to me about it. Hopefully, the ratings system works well. On the plus side, perhaps this means the characters won't have to rebooted and they'll count as canon after all? I can't see why else they'd bother putting the shows on Disney+.