I always considered the load address to be an emulator invention. When it comes to original media, the load address is specified in different ways:
Tapes: First you load some data into the tape buffer (828-1023 on VIC/C64) and that area contains the file name, the load address for the actual file + possible code to be autostarted.
Floppy disks: The first sector of a file contains a link to the next sector, then the load address followed by the file data. I suppose this is from where the PRG format origins, that all 254 data bytes from each sector are used and the first two bytes happen to be the load address. Note that on floppy disks, file names are stored in the directory (track 18 on 5.25") rather than with the actual file data. Load address though is not specified within the directory, just the first sector of the file which makes sense as SEQ, USR, REL etc files don't have the concept of a load address.
Cartridge: Load address is specified by which pins are connected on the cartridge port, a strictly hardware matter.
I suppose in your case the ROM/BIN files are stored on floppy disk as though you just as well could LOAD them and SYS or soft reset the computer to run them, not specifically for use with the EPROM programmer software. If the ROM files instead were stored as SEQ instead of PRG, you wouldn't need a load address. Once the data is on the EPROM, it doesn't know which address in memory it will show up at until it is put in a cartridge or inside the computer where the location of the socket tells which part of the memory map it belongs to.