The number of Google results shows how often a given term is used. If I show you the following numbers for exact results for searches in quotes, you should be able to tell me which represents the more valuable domain name:
37,000,000 exact Google results
436,000 exact Google results
Looking at it from a developer's point if view is just plain wrong. You must look at it from an end user's point of view. A developer is somebody who wants to put content on a domain and get a good search engine ranking. But a corporate domain buyer looks at the size of the market, because he wants to sell something and maybe start a new business. Google search results give you an idea of how big that market is. If you look at the two numbers above, it should be very clear which market is bigger.
Of course, the number of Google search results is only one criterion. You must also look at many other numbers and statistics, such as the number of searches that is performed in any given month, the number of advertisers, the number of yellow page business listings, the average contract value in that industry etc. Google search results is only one piece in the puzzle, but it isn't as meaningless as you might think.
Let me disclose the search terms I used to get the above numbers now: Google finds 37 million websites for "auto insurance" (huge market), but only 436,000 websites for "tree stand" (still a market there, but a lot smaller).