I was programming PIC's way back before MPLAB, and the DOS simulator was really horrible! - never used it, and never used MPLAB either. I got used to programming without simulators, and (for that matter) designing circuits without simulators either!.
In fact I moved to Windows before MicroChip did!, the first Windows version of WinPicProg (still called PicProg back then) was for Windows 3 (before Win95 was released), and was the worlds first Windows PIC programmer - a LONG time before MicroChip made the move.