For it's era it was low cost (compared to 1702 Eproms) and it provided the ability to debug the hardware. Also t was flexible as it was both IO and allowed program entry and crude debug (single step). Early systems also lacked software to interact with and often what was available had the have the IO altered for to match the available IO. This was very true for the 8008 generation and remained true for the early 8080 generation. Later systems such as the H8 were better but also really represented a new subspecies of systems leading to the turnkey based systems. Personally I felt it was the first 6800 (and 6502) based systems that made switches and lights outmoded by using a standard console IO and a rom based monitor program to do the functions that a hardware front pannel provides. By then ROMs/Eproms had dropped in price and the hardware saved was enough made it far less expensive. Allison