Every piece of software that prints direct (other than a RIP) outputs PostScript data. The device receiving that data has to have a postscript interpreter in order to convert that to actual dots of ink. Many indoor (aqueous) printers have build in PS handlers, but there are very few, if any, outdoor (Solvent/UV/Latex) that do.
PostScript is a restrictive output mechanism for a lot of manufacturers, when they can just write a generic driver with a data set that any RIP can communicate with. Also, most indoor printers are used for poster output, where there is a relatively small output data stream. most large format printers for sign work are printing magnitudes larger pieces of data that would compromise an inter PS handler.
Is it possible to have a solvent printer that has a built in PS handler? yes, but it'd be stupid and only work with a handful of design software packages, or it would have to have its own output program that the design program would have to output to, which is what a RIP is anyway.
