Before his company was able to block more of Microsoft's own tracking scripts, DuckDuckGo CEO and founder Gabriel Weinberg explained in a Reddit reply why firms like his weren't going the full DIY route:
“… [W]e source most of our traditional links and images privately from Bing … Really only two companies (Google and Microsoft) have a high-quality global web link index (because I believe it costs upwards of a billion dollars a year to do), and so literally every other global search engine needs to bootstrap with one or both of them to provide a mainstream search product. The same is true for maps btw -- only the biggest companies can similarly afford to put satellites up and send ground cars to take streetview pictures of every neighborhood.”