First, you seem to think that search is a "gold mine". This is completely wrong. Ads are gold mine, but nobody is making much money off of search. Nobody is looking to "pay real money" to have their search queries answered.

Second, you seem to think that Bing is making money. They're not; the most recently available figures show them burning a billion dollars a quarter. That's not doing "well" in most people's books.

Third, a couple of minor points: DDG has their own crawler, and doesn't just repackage Bing's results. On the other hand, Yahoo does just repackage Bing's results, and is shutting down their crawler. I'm not sure why that makes Yahoo "second tier" but DDG a "weird niche search engine". :)