The numbers are already out of date. Google just upgraded 160 million people to Chrome 12. Firefox will hopefully upgrade 200 million people to Firefox 5 this week. I've watch the numbers for the past couple of weeks and IE9 has caught IE7.
The web could really get a bump if we just nudge the remaining legacy browser users to upgrade. Why anyone would run IE6 or IE7 is beyond me.
People still use Windows XP, and people still use old ActiveX software that was developed when IE6 ruled and Microsoft was still pursuing dominance through lock-in.
The real question is why Microsoft hasn't developed a way to install newer versions of IE on the older OS'. There must be a way to isolate the browser from the rest of the system, even if they have to wrap a VM around it.
The web could really get a bump if we just nudge the remaining legacy browser users to upgrade. Why anyone would run IE6 or IE7 is beyond me.