It depends on whether the company is B2B (Business to Business) or B2C (Business to Client)

B2C more often than not needs to support those old browsers, if it's B2B, then in many cases, you can dictate what browsers are supported and what browsers are not.

On our B2B software, we only support the latest versions of browsers (so no IE8, 9 or 10), on the B2C software, we have found that IE8 is less than 2%, so we've dropped support for it, but do support IE9.

If we were doing sales via those B2C channels, then depending on the volume going through that site, we would probably support IE8 as 2% extra sales would often overshadow the cost of making things IE8 compliant.

IE8 is the new IE6, but we have it a lot easier since IE6 disappeared, IE8 is not nearly as bad as IE6 was.

First of all, we need to get one thing clear - IE8 is dying! It's dying slowly and we should feel good about it!

Big companies rely on specific audience, in most cases other enterprise corporations and institutions like hospitals, academic institutions etc. Performing a major OS, browser or hardware change in most cases will be very costly and problematic - they need to insure that every computer on the network works as expected, which leads to even more support expenses. Also, most of these machines are locked down and restricted from installing any kind of custom software.

In the past Microsoft did not play well with the web standards and they implemented a lot of non-standard features in their browsers. MNCs spend a lot of money on developing browser-specific features that work only on older versions of IE.

That said, I see more and more companies transitioning to newer OS and browsers. Microsoft is dropping IE8 support January 2016, which is expected to end the hideous era of non-standardized browsers. Some months from now, this probably won't be a problem to cope with.

Good times are coming, we need to wait a little bit more.

It's simple. Most cases these retard IT admins want to block external access to plugins and other websites. IE8 makes it easy for them. Eventually they will not let users install newer browsers. Plus most cases they are using Windows XP (P.S. Windows 7 comes with IE9.) and these companies won't bother investing on buying new windows licenses.

Depends on whether or not they're in the developing world or not. I worked on several projects for an automotive company and they had to support IE8 because they couldn't force their dealerships to upgrade their computers. Some car dealerships have dirt floors (no joke).