With all due respect, yes you are missing something. It's not about getting disk images to work with emulators. It's about getting files out of Snow Leopard onto real media.
As you correctly point out, no one has been able to produce a real 400K or 800K disk from a current Mac since Apple dropped SuperDrive support in 1998. But that really only affects the Mac 128K through Plus and stock Mac SEs & IIs. Everything else can use a 1.44MB floppy from an OS X external USB drive. But again, that is not the point either. I, as do many others use their contemporary Mac to manage their vintage files, to download from the internet, test them in Mini vMac, and prepare floppy disk images. I don't use a 1.44MB drive, but I do use a USB ZIP drive, for which media easily transfers to my SCSI ZIP drive which I use on a Mac Plus. For the smaller 128K & 512K disks I use Terminal transfer directly out of Snow Leopard. Snow Leopard has now even limited AFP to OS X Macs. The point is, there is no easy way to get files out of Snow Leopard for use on a vintage Mac (either via network or physical media) without one or more intermediary Macs.
Also, SheepShaver nor Basilisk II can use USB devices. There is no implementation for the SCSI bus, floppy, or any other external devices. See the SheepShaver FAQ. Also, whileit is possible on Basilisk, it's not easy or stable, or practical for most. So that is not an option for creating real media or importing real media. SheepShaver (and to some extent Basilisk II) are the only viable methods for reading both HFS & HFS+ images. They make a fine method for managing them, but getting them into and out of Snow Leopard is another matter completely. To do that with any operating system appropriate drivers will have to be written. Although, I do understand that under a Windows PC SheepShaver will access the floppy drive directly (involving HFV explorer), though I'm not sure if Boot Camp will allow that on a Mac.
Finally, there is no panic. Don't over-blow the situation and what some of us are trying to accomplish. It is merely a concern. Apple has eliminated a primary means for managing old media on new Macs. The next Macs released won't even be able to boot into a System that reads and writes HFS, so this is the end of the line. I am a huge fan of Mini vMac because it just works. I fully expect the Mac II emulation (and with a IIfx ROM can run OS 8.1), to be ready by the time Apple likely drops HFS altogether (in 10.7?). Mini vMac will make working with disk images painlessly easy for even the most Unix adverse (I can't stand Unix – command line interfaces were left far behind in January 1984). But there is still no good means to manipulate HFS disk images and media at the moment, without a lot of unnecessary and often unreliable machinations. So why go to all of that trouble? Basilisk II & SheepShaver are not being actively developed anyway, and "dd" in Terminal seems to be rather easy and straightforward method for dealing with this?
Ideally, this is how a disk copy utility would work under Snow Leopard, in case it still isn't clear: Files are downloaded to the SL desktop. Mini vMac can directly import them, or vintage archived files can be put into an HFS+ disk image and transferred to an HFS disk image using SheepShaver. Within the emulator, the files can be manipulated. Using a disk copy utility (like "dd" in Terminal), the resulting HFS disk images can be copied to a real HFS disk on an external drive. Files can then be manipulated and/or generated on a Vintage Mac. The resulting disk can then be re-imaged using a disk copy utility, thereby retaining a single file that can be copied back and forth for use in an emulator in Snow Leopard and a real Mac.