Also, does anyone know why driver updates are not being distributed? It seems a very large number of people have old drivers, but if they visit the AMD/nVidia/Intel website then newer ones are available. Why aren't those updates going over automatic update systems like Windows Update? That would help significantly with the WebGL driver problem.
On OSX, Apple usually doesn't update graphics drivers (much) in the current version, and major driver updates only arrive in newer versions of the OS, with older version not being updated at all anymore. Most people never update their OSX from what they have, but they'll buy a new machine eventually, having a new version it. For Apple, driver updates for their desktop style products is directly tied to their hardware sales turnover.
On Linux drivers are a very mixed bag of goods, some users have up to date drivers, others don't for a variety of compatiblity/bug reasons.
On Windows machines you need to differentiate between 3 classes of machines:
1) The enthusiast users who usually get their own machine (or build it) and install windows on it by themselves.
2) the OEM home users, who get their systems from the likes of Dell and HP
3) The business users, who get their machine provided for them by the IT-departement of whatever company they happen to be in
Enthusiast users enjoy full admin priviledges on their machines and they often have updated drivers. However, a lot of those users are still using Windows XP, and driver vendors have sort of stopped providing drivers for XP since it'll soon reach its EOL, leaving a good chunk of these users with no viable upgrade path than to install Windows7 or Windows8. On any account this is a minority user group.
OEM Home users get their machiens with extensive modification of the OEM which include changed update procedures, OEM specific bloatware and restricted admin priviledges. OEMs do this in order to provide unified support. They don't want to have to deal with a whole Zoo of issues as every user customizes his machines software. Consequently they make it difficult to do that, and often claim warranty void if you modify the software. OEMs are notorious for not updating drivers, ever. Again this stems from them not wanting to deal with a Zoo of issues. Unforunately a large portion of Windows users are OEM users.
Business users do usually have no admin priviledges, and the IT departments of companies do not like to update their machines, ever, except for security patches. The update policy of those users is set by the business realities of the IT-department which tries to keep the corporate desktops secure and running with a minimum of effort. Updating drivers to get 3D working, which is not considered an essential business function in most companies, is therefore a net-loss activity because it does not deliver additional business value, but it costs money to keep drivers up to date and might throw up more work in case of the drivers introducing security issues and other support cases.
For these reasons, the vast majority of desktop-style computer users never get driver updates, ever.