But the issue here is that you are comparing fundamentally different pieces of technology, and yes, yes, a smart phone is a computer too, but I don't see anyone using them for general purpose computing right now and to be honest, I don't see it any time in the future.
Go in to any office, literally, any office, and you won't find anyone working on an iPad or their Samsung Galaxy, they will be working on a PC or a laptop, most likely running Windows and for the most part they are happy with it.
Comparing the sales of Windows against the sales of Android is like comparing the sales of Toasters against the sales of Microwaves, sure, they might be at some level similar appliances but they are used for completely different reasons.
A smartphone is used for consumption, it is a luxury most people have or aspire to have and while the PC or Laptop may fall in to that department at home, in the office, they are used for creation (except from when we are bored of course...) and for the foreseeable future, that's how things will remain until the space is completely "disrupted" (whatever that means.)
I'm going to put it like this, I don't live in Silicone Valley, I live in a small town in the north of the UK, and every person I know and who's house I have been to. Every single one has both a smart phone and a PC, that's not just me saying it, that's every single person.
The reason why the numbers are so different is something crucial and so simple that we always seem to overlook it:
Normal people[1] only need one computer for their home and they share it, but they want to be in contact with their family via phones at all times, and the kids these days don't want a Nokia 3310, they want the newest, most expensive model, because they are COOL.
You can attribute it to whatever merely visible swing in the market you want to, but that is the simple truth.
[1] - By which I mean people who aren't in the tech industry.