Large companies tend to be bad at keeping up-to-date. I know of a bank that still uses OpenOffice. No, not Apache OpenOffice: they still use the real OpenOffice.org.
Workstations are often locked down, so employees can't install or upgrade anything.
Workstations are often locked down, so employees can't install or upgrade anything.
The second most popular version? IE 6. Not even 8. IE 6.
Who still uses it? Employees of other government departments...
(Disclaimer: I work on analytics.usa.gov.)
It gets worse... People write apps that use Flash (online training) or Java applets.
There are solutions to this, but none of them involve using the one true SOE, one SOE to rule them all!