I can think of 3 reasons:To be honest I have been using DuckDuckgo for 2 years and it almost never happens that I do not find what I was searching for.
I honestly don't understand why more people don't switch.
- Habit (if the default works, why change it?)
- Not knowing how to change the default setting (most people don't venture into settings for fear of breaking things)
- Fear of being different from everyone else (look at how people are ridiculed for using Bing - which in my experience has been pretty good, but my default is DDG <- ha! see! even I have a little fear of being ridiculed for just mentioning Bing 😅)