I can't speak to the other companies, though I know google want's "all the worlds info at your fingertips" which is a reasonably high ideal... I can speak to what Apple is doing as someone whose followed the company closely for a couple decades.
Apple doesn't care whether you buy the 3.5", 4.0", 7.85", or 9.8" screen.
Apple is bringing the personal computer to the 6 billion other people who weren't able to get in on the PC revolution.
Their slogan in the 1980s used to be "The Computer for the Rest Of Us." While it isn't used for marketing, the mission hasn't really changed.
There were two key issues that prevented those people from participating in the PC revolution.
The first was that you had to be trained how to use a computer. You had to be at least literate, and you had to spend the time to overcome the significant usability hurdle that even Mac OS X presents to the random person. (Eg: your grandmother.)
iOS has revolutionized computer usability such that your grandmother can use it, even if she never made it to high school (bless her heart.)
The second is price/distribution. PCs were for the relatively rich. And while Apple never seemed to compete on the lowest end, that's simply because most people who think Apple makes expensive products think about $300 laptop as "affordable". Instead, Apple put a $50 computer in peoples hands- the iPod shuffle. Sure, it might not be as full featured as a laptop, but you have to walk before you can run.
Lets also not forget that there's a big difference between a PC that draws serious amps and thus needs a house wired for electricity... and a mobile that runs on batteries and can be charged with solar power.
Apple is toiling away building the greatest development/ design/ manufacturing/ distribution machine in history. Of course they have some key partners in this- foxconn and their suppliers.
That iPod shuffle has been replaced with the inexpensive iPod touch, which really is a PC. And of course there is the iPad mini, also a new entry on the low end pc market.
Just because they didn't choose to make zero margin crap that nobody can use (Eg: windows running netbooks), doesn't mean they aren't working their tails off to address this under filled market. They are coming in from the high end, which makes sense given that they can't make the devices fast enough. Hence scaling the company across all those axis I mentioned.
I'm sure this sounds like a radical idea, because "everyone knows" that Apple is only interested in selling "shiny things to rich people". Just keep thinking that!
Whether android ultimately beats them to it, or not, their mission is pretty damn noble, as far as I'm concerned.
The post-PC era they created is going to empower a massive number of people.