I think it would be great for them to switch but I can think of 2 huge reasons they wouldn't.
1. Retraining the users, very few people use linux so it would be a massive undertaking to retrain their thousands of mostly non-technical workers to use a new, unfamiliar, operating systems.
2. Microsoft Office. Say what you want about LibreOffice and OpenOffice but when it comes to enterprise grade software MS Office is unrivalved, especially concerning Excel.
3. And whatever other IRS-focused enterprise software they may be running, probably runs on the Windows platform.
Side note: Maybe this gets better in 10 years when lots of things have been written on the managed CLR? Although I don't think the challenge Wine has is running the C++ programs, but implementing all of the stubbed out APIs correctly... the same challenge exists with a C# interface.
4. As good as Ubuntu's latest version and its UI may be right now, anything other than basic stuff you want to do requires command prompt. Normal users who are not geeks can't imagine themselves doing that on a daily basis.
Still wondering how they even go by doing their job on a computer. If you ever worked in a support role, you'd know that no matter how many years of experience they have, they are most likely being confused by the UI change every time MSFT decide to be 'cool' and 'innovate' (See the ribbon style introduction back in 2007). And this is without the regular nagging of them not wanting to learn where are the options they want to modify, despite the menus and sub menus.
With regards to MS Office and MS mail client, sure they are more polished, but does that really matter? Are those people crafting an art piece every time they want to add an image to their report? Just an honest question.
3. Microsoft Outlook. If you've worked at any of these big organisations, you quickly learn Outlook plays a big part in day to day running of the office.
1. Retraining the users, very few people use linux so it would be a massive undertaking to retrain their thousands of mostly non-technical workers to use a new, unfamiliar, operating systems.
2. Microsoft Office. Say what you want about LibreOffice and OpenOffice but when it comes to enterprise grade software MS Office is unrivalved, especially concerning Excel.