For me personally, nothing, apart from “I use it on other devices so I’ll use it here too”.
Moved from Google to DDG a few years ago, I have no reason really to move to another search as i’m satisfied with duckduckgo, but i’m eyeing Kagi.
DDG has been fast, responsive, works fine when proxied via a datacenter IP (unlike other services that start throwing capchas at you), looks familiar/like Google to the untrained eye, and image search works as you’d expect. If you’re coming from google, to be honest there’s no reason to pick it specifically, there are a wealth of search engines to choose from.
Approaching it with google-style searches often yields shit results. My search style adjusted over time, and now I find it much better than Google for my use.
As a sidenote, I’ve found Searx and Yandex are better for niche/unpopular sites (especially those with user-submitted content), as well as 🚢🏴☠️.