Crawling the web is expensive, barrier to entry is very high.
Many alternative search engines claim to have built their own crawler, however their coverage is small and they have to fallback to Bing or Google.
You can actually check this btw. The results on Bing are identical to DuckDuckGo's in many cases, which are often inferior to those of Google. When different make sure the "location" parameters are the same and clear Bing's cookies, although local searches are absolutely terrible in Bing/DDG anyway. But they sometimes diverge on some queries, either because DuckDuckGo's cache is not up to date, or because it had relevant results in its own index.
But yes, if Bing closes its API, DuckDuckGo either switches to Google or it's dead in the water.
Many alternative search engines claim to have built their own crawler, however their coverage is small and they have to fallback to Bing or Google.
You can actually check this btw. The results on Bing are identical to DuckDuckGo's in many cases, which are often inferior to those of Google. When different make sure the "location" parameters are the same and clear Bing's cookies, although local searches are absolutely terrible in Bing/DDG anyway. But they sometimes diverge on some queries, either because DuckDuckGo's cache is not up to date, or because it had relevant results in its own index.
But yes, if Bing closes its API, DuckDuckGo either switches to Google or it's dead in the water.