To be fair, when IE6 was launched it wasn’t that bad compared with the alternatives. Netscape 4.x was far worse!
The problem started when Microsoft arrogantly decided that IE6 was the ultimate browser, and stopped all development on a new version. This was around about the time when the standards movement started to get momentum, and Mozilla and Opera were putting the browser wars behind them and moving towards interoperability.
Microsoft has never supported interoperability. They are the dominant force in the desktop computer market, and they want to maintain their monopoly position by preventing other companies from successfully entering the market. That is why they are always pushing proprietary formats, it’s why they were pushing Silverlight, it’s why Outlook 2007 fails so spectacularly to be compatible with any other email client.
By the time Microsoft realised that they couldn’t just let IE6 continue as it was, because other browsers were overtaking it in technical standards and were really eating into its market share, they were so far behind the curve that it has taken them 5 years to catch up. Even with IE7, it seems like they weren’t interested in making it meet standards, and they hadn’t realised the depth of feeling against not just MS IE but the whole idea of a web browser that ignored web standards. Now they are stuck with the unenviable task of making software that both works according to the standards but doesn’t cause too much damage to the crap that we were forced to write to cope with older versions of it.
Alot of large companies local intranets relied on IE5, IE6 when newer versions of IE started being released (7, 8 and now 9beta)
Large corporations are slow/hesitant to upgrade entire intranets as it is costly in both time and money.
Since the release of IE7 there have been great improvements in the rendering capabilities of that browser. Even better with 8 and as far as I know 9 is/will up there with the rest of the browsers.
So it really isn’t a problem of M$ not updating their browser (it was for awhile) but getting users to upgrade due to the above mentioned, old comps that will not run the newer versions and people that just don’t have a clue what browser they even use let alone that a newer version is available is the real issue.