Apple and Microsoft are different in a lot of ways, but their core business is making operating systems for personal computers. Apple makes the whole widget, but Microsoft focuses on the OS and licenses it out. Different business models, but much the same business.
It's not surprising that Apple and Microsoft, as a result, have the two best Phone Operating Systems as well as the two most popular Desktop operating systems.
What is google's core business? Advertising. What is Facebooks? Advertising What is Amazon's? Retailing
All of these, of course, have some overlap with Apple and Microsoft. Amazon is increasingly selling digital goods, Microsoft got into the search business (a failure that is illustrative of my point, btw.)
What is the key value add that Facebook can add to a phone that nobody else can? Deeper integration with Facebook. Is that compelling? For a phone? Certainly useful... but why make the tradeoffs?
The same thing is true with Google. The original iPhone shipped with google in every place it wanted to be-- providing maps, providing youtube video app, built in, as the only option for search, and consequently, also, the primary mobile advertising opportunity.
Apple didn't try to keep google out, Apple partnered with google, at a very high level, and gave google unique access to its device. I cannot think of any other company whose key products Apple ships as default on the iPhone. Apple's still shipping google maps (or actually Apple Maps app, backed by google) But, notice, despite the deep integration of Twitter in iOS 5, Apple doesn't ship the twitter client.
Even before there was a third party Apps business, Apple gave Google premium positioning for its services in the OS.
What does google have, fundamentally, to offer to the phone industry that nobody else can offer? Better search? A better maps app?
As I've pointed out, Apple let google have prime real estate to get that distribution. It is only after Google decided to compete with Apple that Apple bought an advertising company, and started buying mapping companies, and started offering Bing and Yahoo as alternate search engines in Mobile Safari (or maybe I'm wrong and they're not even doing that, can't remember.)
Success comes form being focused.
Facebook is increasingly becoming very distracting and kinda pointless. The things my friends share that I care about are buried, and Facebook arbitrarily decides not to show me many status updates from some of my friends.... meanwhile BS is at the top of the feed all the time.
Google's search results are in a marked decline. The advertising business is going like gangbusters, but Google is getting less and less useful as a search platform.
And now they're going to start making their own hardware?
Further, what's the business model? Apple and Microsoft have been very successful selling operating systems (though Apple packages them with the hardware.) Nobody has been nearly close to as successful giving away software for free. Google and Facebook have to plow most of their R&D budget into their core businesses, so they can't compete (and in googles case, so far haven't' been able to compete) with Apple (and to a lesser extent, Microsoft) in adding key features to their phone operating systems.
I think the folly of Apple, trying to make its own desktop CPUs is another good example. Even when partnered with Motorola and IBM-- two heavyweights-- and a superior technology base-- they were unable to remain competitive with Intel simply because Intel is able to plow so much money into their CPU business.
The CPU Business is core for Intel. The OS business is core for Apple and Microsoft. The devices business is core for Apple and Microsoft's partners. IT isn't for Google, Amazon or Facebook.
They might be successful making phones, to some extent, but they will be taking their eyes off the ball when it comes to their core businesses.