PS and EPS figures have been the bread and butter of astronomy for decades. In turn, the astronomy journals accepted the PS and EPS figures for publication. Recently, plotting packages are supporting PDF files more than the EPS and PS formats. An EPS file was originally developed as a language to tell a program how a page should look.
You could look at the PDF format as the next step in the evolutionary chain to the PS/EPS format. PDF files can contain additional information that EPS files cannot such as transparency, better support for character encodings, ability to embed TrueType and OpenType fonts, and more. With the more modern plotting packages, you have more flexibility about your figures when saving in PDF format.
Surprisingly, PDF figures are not accepted by several astronomy journals, but there are exceptions like A&A and MNRAS. Because of this many researchers are investing a lot of time to convert PDF figures to PS/EPS format for publication. Because the conversion between PDF to PS/EPS is not perfect, getting the EPS file to look right can be frustrating and time consuming.
Hence, a few astronomers (David Hogg, Thomas Robitaille, August Muench, and Eli Bressert) got together to start a petition to let the publishers know that many of us prefer to give our figures in PDF vs EPS format. We don’t want the journals to cease support for PS/EPS figures, but at least accept PDF figures as a viable format. If you want to join us in getting this message across to the publishers please visit this link to support the petition.