The failure of led buttons is partially on me. The reason to do it is to have the used buttons like up, with the cabinet correct color depending upon which game you've loaded. controls.dat kind of fell apart so there isn't a good way to get that data anymore. I know headkaze has some solutions as does the guy that does ledblinky but honestly none of them, controls.dat included, are easy to use, ideal solutions.
Point is, there was a useful purpose for them, it just kind of got lost along the way.