Ask HN: Why do big companies and clients insist on IE8 support?

I think the question is more about 'old' customers rather than 'big'.

The reason most of the time is that the company had a bunch of apps/websites built in the era of IE6/7 maybe even IE8, and they need to be able to run in compatibility mode. It is cheaper for them to stay with old IE than to have these apps re-written for modern browsers.

Hopefully we're nearing an age where the cost of maintaining these old systems is starting to be more painful than upgrading, but I'm sure we'll continue to see old IE requirements for another 5-10 years.

They have legacy applications, written in the late 90s, that have been maintained barely alive because they are linked to a critical process like supply chain, pay, etc, and they still require their employee to use the most ie6 compatible browser.

It is always cheaper to ask the new application to be backward compatible with the environment, rather than upgrading all the legacy ones. But this is also the surest way to dig your grave deeper...