The majority of their user base doesn't know and wouldn't care about this type of thing even if they did.
Source: I'm a family "computer whiz" :/.
People understand if a system is insecure, and now apparently all non-Yosemite Macs are insecure. Folks will grok that. Whether or not they find out about it, well that's up to you and I, and everyone else on this website.
I agree it's up to us to proactively tell our parents, friends and colleagues who may be vulnerable about this problem.
An additional bonus is that you can get these things for free if you know where to look.
Of course, being 11 years old it also has its drawbacks. It won't fit more than 2GB of RAM. It is based around a single-core Pentium M which generally performs fine but shows its age mostly when meeting Javascript-hobbled web-related things.
BUT... and this is one of the main reasons why I use older hardware... if you develop software on this machine, and it works fine on that machine, it'll run circles around the stuff your neighbour made on his latest FlitzBang Fruitmachine. It'll but cause a blip on the CPU meter where his (or her, your choice) result maxes it out. It'll use memory like it was rationed, not like it was on sale.
Of course you can not develop software for the dark side on this older hardware. A small loss, in my opinion.