I think your calculations are a bit off. For all the people licensed to use linux, you are going to need ~99.9999999833% of them to care about just one bug and have the ability and desire to fix it for the entire user base to benefit.
May not seem very efficient, but it is positive sum.
For the sake of argument, lets just say 100% of Americans care about health care and fiscal responsibility. Hmm... my bet is a couple high school students will do a science fair project that will successfully demonstrate safe clean nano scale cold fusion technology before Social Security and Medicare get a balanced budget that is properly secured for future obligations.
Of course, you say users don't care about open source in a practical way. Well duh; if they cared in a practical way, they wouldn't be called users, they would be called developers. So all you really need to ask yourself is 1) Do developers care about source code? and 2) Should users with a spark of intelligence and ambition have it within their ABILITY to become a developer?
Proprietary Software is akin to the scribe culture of long ago, where certain people read books to most people. Few people could read, and very few could write. Either way, paper was very expensive. When the printing press came along, and books started becoming cheap, books became open source; ordinary people, not just those of an elite class, began to read. Quickly came the age of enlightenment, as more people began to read, so did many people begin to write.
So I ask you, why do you need the source code to your books? Are you going to fix problems in stories and notify the author? Are you going to write a novel? Of the install base of books in homes, how many of those do you think have taken advantage of the open source nature of those books to write a book of their own outside of academic circles? Inexpensive open source books have been around for a few hundred years, though writing and libraries have been around for thousands. Digital computers have been around for about 70 years, but was restricted to a fairly elite class of people such as university students. Open source software in the 90's was much like the way scientists share their information with each other. Servers based on open source software became very popular with the birth of the Internet, and Linux for the non-geek really started to make an appearance about 2004 with OpenSuse followed by Fedora and Ubuntu. Non-geek / non-business people only just starting to get computers... early 90's? Computer literacy (basic usability) becomes mandatory at just about every job by the late 90's. With the Internet, and the human readability of html, everybody was making web pages with about much class and style as a 4 year old writing his first book half way into his kindergarten.
Computer literacy is VERY important. I would like to hope that everybody feels it is within their ability to learn and contribute to an open source project if they desired to. I have known adults that do not have basic reading comprehension. Some are embarrassed, but many just don't think it is important or relevant to their lives, though I think it has been at least 10 years since I have heard that argument from an adult. We can either have a class structure of producers and consumers, programmers and non-programmers with the programmer class picking who will move up to become a creator, and who will not, or we can recognise that good software does exist and improve for its own sake as it serves people.
You can either create a class system (proprietary), Give people the freedom to choose whether or not they want to support the class system (MIT/BSD), or fight the system with hostility and dogmatic ideology (GPL).
Most people don't care how their computer works any more than their care, their house, or even biological functions. But when it comes to using that as an excuse to keep that information away from people, I err on the side of hostile dogmatic ideology.
I guess it can depend on who you mean by purists necessarily, but if by purist you mean those that don't believe in mixing GPL and proprietary software (LGPL aside), you think the FreeBSD is really all that thrilled with the wonderful and great contribution of MacOSX by Apple? Is there, or does it matter, if there is a FreeBSD/Apple development community, or are they totally separate? I think the perception of the development community over just those questions is in part directly responsible for the growth and cohesion of the Ubuntu Development Community. I also believe Ubuntu has done far more to promote and improve Debian and Linux than Apple has done for FreeBSD or BSD.
I guess there may be too many sides to it, because just like driving a car, many people just want to get to work. Is literacy or should literacy be important? Open Source software is a very new thing in many ways, especially if you compare it to things such as books. But look how important "software" has become in the last 15 years. Phonetic language and mathematic language literacy has been considered very important for some time now as being a necessary part of learning, self improvement., and personal responsibility. I think computer programming literacy is getting up there as things people should really start looking towards as a basic educational tool, and open source is clearly a vial component of that movement.