They get better, but the base is their search algorithm, capacity and ability to attract business. As fragile as this can look, it's much stronger than the sight of an iPhone upgrade going on for years and feeding the biggest company on earth. Nobody says Apple will go bankrupt, what I say is soon or later, sooner than later, the iPhone concept will be obsolete and they haven't shown other genuine revenue stream.
There aren't that many different search algorithms out there. All engines use a variation of one or the other. Bing isn't worse because it's based on a worse algorithm than Google. Neither is Duckduckgo. They are just used less.
Btw Apple's other revenue streams like the iPad and the Mac are still more profitable than Google even though you think they are not genuine.