I don't think it matters, roughly half of browsers have it on and half have it off. The most important thing is to not change it from its default since thats the real marker trackers can use.
DNT was an entirely pointless idea. Given the easy choice, no one wants to be tracked when not being tracked is an option so browsers rightfully started making it the default since its what everyone wants. But no tracker is going to think, gee, no one wants me to track, guess I'll shut down my business so they ignore the marker or use it as another tracking point.
