In many cases they can. Text representations of binary flash data has three advantages:
1. It allows the address to be given as well as the data.
2. It allows CRC validation of the address and data.
3. It can be transmitted and saved in all communications system.
Consider a large device - say 8Mb but you only want to program the last 16 bytes, a 'flat' binary file would have to include the whole device but the address of the final 16 bytes can be specifically given in the 's' file so the programmer can go straight to that location.
Brian.