I would like someone to make some objective research on that.
My experience is the reverse, so I strongly suspect our reticence is just one of changing our habit more than an real thing.
I switched to DDG years ago and it took a few weeks to wean out the tendency to compare searches, usually brought on by the fear of missing out something.
I very rarely have to resort to a !g search and usually if I can't find it on DDG, I won't easily find it on google either.
I don't feel like missing out on anything and I always find what I need (and if I don't, I can't find it in other searches either).
Other platforms have some strength in some area, like Bing and Google have more tools for image searches, and it's possible that one of these is better than the others at some specific domain, like research papers or patent searches.
But after switching to DDG, all these options are still available and -at least in my case- 99%+ of my needs are met with it.