And they shouldn't have to. Developers should support their working equipment by updating drivers. They've known about the transition to 64-bit for years and it's not something that can just be ignored because all the hardware is now 64-bit. It's not like this was done on a lark.
This was addressed earlier in this subthread. It's not just an upgrade to 64-bit — they're also changing the low-level interfaces, and the new ones are apparently not well documented. So while it probably wasn't done on a lark, it doesn't sound like it was done in a very well considered manner either.
True, but a lot of those devs ignored the 32- to 64-bit transition for so long that now they're having to do both at once. Authors that moved to 64 bit several years ago have a lot more free time right now to concentrate on supporting new APIs.
The low-level interfaces in question were changed almost 4 major versions back. There aren't any new interfaces or APIs that haven't existed for 6+ years already. The only people complaining are the ones that procrastinated because Apple continued to support their outdated apps.
Apple introduced new low-level interfaces four major versions back, and Apple couldn't work up the interest to document them in the intervening years, and then Apple decided to cut off the interfaces that are documented, and somehow any problems resulting from this sequence of choices Apple made are the fault of third-party developers for not jumping to new technology that Apple didn't care enough to document? That interpretation of events seems a bit obsequious to Apple.
If everyone should have been prepared because this change has been in the works for so long, then surely it's inexcusable for Apple to have left the new stuff in a poorly documented state all that time. If you do feel that Apple's lack of preparation is reasonable when they had even more warning than third parties did, then it seems unreasonable to fault developers for also not being prepared.