Reading this excellent question regarding logo export formats, and it made me want to ask a question that was a little bit more narrowly focused than that one.
I know when to use a GIF and when to use a JPG, how to optimize certain raster images for certain scenarios. But I feel like the only reason I ever use EPS is because "that's what you're supposed to do," which isn't really a good reason.
So, what is the purpose of an EPS format? What does it do that AI, PDF, and SVG formats do not?
In my experience, non-technical people don't need EPS files, they need JPEGs and GIFs and maybe PDFs. Other designers will almost certainly be able to handle an AI file, and can definitely handle a PDF. For the Web, SVG and PDF make more sense.
The printing realm is one where I'm really not that experienced, so I can't speak to that.
Is this a legacy thing? A compatibility thing? Something for the Quark crowd? Or is there a real benefit that EPS brings that other formats can't do? Would anyone in the audience be hurting if he or she could no longer export to EPS?
More on unique features of EPS. PDF is a distilled EPS , that is all the intelligence the EPS file contained has been stripped away. For example, since the EPS is intended to be executed at the printer or RIP stage it can use the printers settings. So the logo could decide to print a specially made black and white version instead of printing a grayscale version of the color logo.
Now the distiller didn't just do the transparency flattening, it removed the code in postscript and replaced it with static primitives. Off course if you used a editor like Illustrator that's what your EPS contained anyway so no loss there for a typical graphics designer. Theoretically however EPS could contain anything even including transparency the target rasterisation engines couldn't understand this tough so your postscript would need a lot of code handle this. This brings us the biggest problem of EPS.
EPS was never designed to be a transfer format between graphical applications. It was just intended to be a conduit for you to talk to a printer. A lot of it's features are unnecessary in a graphics design context. Worse there's really no rules on how the EPS file would be interpreted when machine read back. Therefore if your EPS had any custom processing they would be lost once read into illustrator. So while all of the data is in the end rasterized in a printer pipeline. And a custom primitive that itself rasterizes at full resolution just like any other vector graphic there would be no way to retrieve that info in a editing application without raseterizing it to some custom size, while the eps itself could have rasterized it for each printers maximum resolution. But alas not if you open it for editing in between.
EPS has mostly, and I say mostly, superseded by PDF. PDF is a direct successor of EPS. Likewise SVG is heavily influenced by EPS (maybe too heavily in fact). But we are still quite far away form not needing EPS. Need a 2d barcode, use EPS. Need to dump something out of your program? Use EPS, its easier to craft than PDF but 100% compatible with one. Need custom printer features, use EPS. Need a logo that prints different each time? Different on each page? LATEX user, send EPS etc etc.
The last remaining big reason to use EPS is rather surprisingly the following: Normal users can not embed PDF to their documents. There are several reasons for this most notably that normal users have been taught that PDF is final format and can not be reused. Then there is the MS word issue, which believe or not is quite common with normal users.
EPS is a great format, but its maybe too good for its own future. It actually competes with adobes long term goals in a non healthy way as far as adobe is concerned. So yes its a bit of legacy that no current format comes near to replacing. But in manualy done automatic work pipelines PDF way too complicated. So no matter how legacy the format is for somebody working on Adobe stack, one fact remains elsewhere it is often the only viable option.
Bonus feature: For a designer EPS is the easiest way to get into graphics programming.