Thanks for the ideas, everyone. I tried running a worksheet with similar figures in Maple 13 Classic, and it output an eps file that *does* have these commands in it. Then with a little tweaking, I got the axes thicker. Now I need to go back to the paper figures and see if I can get them tweaked properly.
This may be a successful workaround this time, but my copy of Maple 15 does not have Maple classic with it, so this tweak is not going to be available as people continue to upgrade their software. Maple really does need to do something about this. A colleague of mine told me he has the same problems with his group at Sandia -- they won't use any eps exported Maple graphs he generates because they are unusable in research papers.