Even though Unity and other desktop environments are quite intuitive at this point, changing over would cause a massive disruption to laymen who have been using a Start menu, Windows Explorer, and Outlook for years.
The benefits of switching (license costs, I suppose) far, far outweigh the benefits.
Ubuntu, Suse, and RHEL are commercial support. Novel, Canonical, and Red Hat make good chunks of profits from support contracts. They have a business model at all because of businesses that adopt them and pay for support, and Red Hat is a billion dollar business!
Note most of that support is server side, but I know all 3 offer some variant of standard desktop support as well. So do a lot of Ubuntu PC vendors like system76.
I can't be bothered to post links to every distro and every consultant on the planet, but just for laughs:
http://www.debian.org/consultants/
And this is just independents (mostly) and just Debian. I'm sure IBM and other major corps would be glad to help as long as its legal, which is not an issue with FOSS unlike windows.
Now if MS opensourced windows XP as part of the abandonment, that might be interesting.
The irony of that line in a discussion primarily about microsoft products is fairly humorous.