Actually, the problem with many of these markets is the winner takes all nature of them. Google is significantly better at obscure searches as compared to Bing

Actually, the problem with many of these markets is the winner takes all nature of them. Google is significantly better at obscure searches as compared to Bing or others. A large part of the reason is that Google gets a lot more rare search terms being the default, and it improves by learning on which links do users click on and what following searches do users do to fine-tune their search. A less frequently used search engine misses out on this data and consequently doesn't improve.