DDG is probably worse than Google, but often it's good enough.
The !commands allow you to search more specific sites directly - if I know I want Wikipedia, which I often do, I can just type !w and search it directly. Similar for other things like IMBD, Wolfram Alpha, etc. It's just a convenience.
You can also search Google using a command, which is sometimes necessary when you're really crawling the depths of the internet for something old or weird, but nine times out of ten the straight DDG results will get you where you need in my experience.
