First, all I have to do is set up DDG as the default search engine in my browser, and then I get tons of search shortcuts working without any more effort on my part. I don't have to worry about syncing between different computers, browsers (I use Chrome and Firefox at different times), and operating systems.

Second, there are many more shortcuts than I'd ever think to maintain myself, and somebody else has already put the work into defining them. I can do !{relatively popular site} and even if I'm guessing, it almost always works. (In fact, I can't remember the last time it didn't.)