I switched from DDG. It saves me more than $10/month, both in time and in actual dollar costs due to suboptimal search engine results. It’s as simple as that.
The jump in improvement from google to ddg is probably bigger than the jump from ddg to kagi though. Also, I switched before ddg and kagi had AI search. Kagi’s AI is a huge differentiator for me, and I haven’t used the DDG one that much.