PostScript is a page description language for print publishing, first developed by Adobe in 1982, and it was a key part of the rise of desktop publishing. Because PostScript programs could be processor-intensive, actually rendering the page was beyond the capabilities of many computers of the time. (When it shipped, Apple’s PostScript-capable LaserWriter, with its 12 MHz 68000 processor, was more powerful than the Macs of the time, which had only 8 MHz 68000 processors.) To make working with PostScript files easier, Adobe and Aldus, makers of PageMaker, developed the Encapsulated PostScript file format in 1987, combining a PostScript program with a low-resolution preview of the content. EPS was a popular format for the print industry for some years, until PDF supplanted it in the 1990s.
Neither PostScript nor EPS is used much today, but if you still need to view and convert files in either format, Apple suggests that apps that can work with .ps and .eps files are available “in the App Store and elsewhere.”
If you just need to convert an occasional file, there are numerous Web-based conversion tools, including CloudConvert, which handles both formats (among many others) and provides up to 25 conversions per day for free.
So although it’s too bad that Apple chose to drop support for these files in Preview in Ventura, it shouldn’t be difficult for those who still work with the formats to develop alternative workflows.