And in general, it's not. But certain platforms (e.g. OS X on PowerPC) have been artificially restricted to the point where no new browsers are being made for them, so the latest version you can get to on them is probably outside of Google's scope of support -- and if it isn't now, it will be shortly. For instance, sure, a PowerBook G4 isn't necessarily powerful by today's standards, but surely it's powerful enough for Google Apps, yet today I don't believe it's supported in the current version of any browser because of its inherent OS X 10.4 or 10.5 cap. Sure, it's possible to switch to Linux, but I don't personally believe the user should have to.
In essence, upgrades are not as simple as you may think due to forced platform incompatibility/vendor lock-in. Forcing an upgrade like this can cost users a non-trivial sum of money on top of what you're already charging for the service!
So while I appreciate the moving into the future, I feel bad for the people whose wallets are going to feel the pain of such a move.
Didn't you also bring that upon yourself by buying a product from that particular vendor (Apple) as opposed to any other? Upgrade treadmills and forced obsolescence are always a risk with software, and users need to learn to account for it.
I recently acquired a Macbook Pro from work, but I'm using Windows 7 on it full-time. I'm far too wary of being forced to upgrade when Apple stops providing security updates to the version of OS X currently installed on it.
Banks and financial institutions are subject to extensive document retention and security regulations -- using Google Docs is out of the question. Of course, that is one of the primary reasons why their upgrade paths are so slow.
they have slow update paths because they can get away with slow update paths. if web developers stop catering to lazy IT departments, maybe they won't be so slow anymore.
They have slow update paths because they've spent a lot of money on in-house middleware that they don't feel a need to update, and sometimes those systems don't work so hot on the new browser. Faced with a choice between updating old middleware and not updating the browser, they choose to wait on updating the browser. The longer they do that, the more work the middleware needs to be "up to date", and the worse the problem becomes. Definitely not isolated to banks.