Sorry, but you're wrong. I've actually worked as a software developer for an ISV, and it's always about resources. You only have a given number of developers at any one time, and supporting multiple versions takes more work, more space and often going back to fix old code takes your best people- who really want to work on the new stuff, and who make you your best money when they do and who'll leave if they're stuck fixing old crap.
Public companies are in the business of getting people to upgrade- if that's a surprise to you, then I'd be surprised. If you choose to give them your money instead of investing in say Open Source software, then you reap what you sow.
You can also argue that Apple's had Adobe's software for years, and could have ensured compatibility- they're coding new stuff anyway, and you can always make a new API instead of breaking an old one.