MD
I can confirm from experience: of teaching people in the groups that you listed, that your points are fundamentally correct.
The Rev Keef accurately described the circumstances of some of his support community.
Don't bait Mixture; the avenging Angel of the IT Apocalypse, his perspective is technically valid and comes from experience and concomitant commercial responsibility and all that it entails (no pun intended). Remember he/she is taking the trouble to post useful info on PPRuNe.
M$ are exploiting their Monopoly as any rational commercial Company will do to placate/maintain their Shareholders.
They could have provided an easier/cheaper upgrade path for their XP users to Win 7 to maintain their XP user base.
Old Kit will run Ubuntu/Mint/Fedora very efficiently, but the rub comes with the peripherals and the user facing interfacing software design.
Printer Support for the uninitiated ? Wi-Fi Grrrrr. Plotters.... and installing re configuring software.
Untrained, poor (in all its forms), That's where XP Wins unfortunately.
To all the techies out there remember where you started from and you will begin to understand the scale of the problem - we are talking Millions of users world wide.
CAT III (Techie of sorts).