Excepting the dimension of privacy, none of those alternatives are as useful or capable as their mainstream competition.
Are the results as good? Probably not. But there's always a trade-off we make when choosing our tools. It's not always about choosing the one with the most features or the one that's most popular. Sometimes ideology matters, and I'd say that's the case for many who choose a search engine like DuckDuckGo over Google. I'm more than happy to trade not-quite-as-good search results for privacy – and I know that the more people who do, the better those search results will become.