More in the realm of other reasons. Transistors of the day could not switch much current so I^2R ruled where higher voltage at the current they could switch was used to get enough power. This was balanced against device breakdown voltages. Other factors that are to be considered is higher voltages allow larger signal swings for better noise immunity at the cost of speed (R*C). Forget batteries. The voltage stability will be important and as you get enough powered elements you'll find that all those milliamps start to pile up to amps, potentially lots of them. I'd stick to 5V for interface to current parts where needed but you might find time to look at old machines and their design. One of the things done was -V to reverse bias transistors to help with stored charge for faster switching. The -V was in the range of -3 to -10V. The most recent of transistor machines like the PDP-8 (link-8 too as well as early DEC modules and the TX2 machine) would be an example to look at. FYI: the really ond machines used PNP transistors as the Germainium technology was better able to make those, that only means all the votages are "upside down" compared to what we currently expect. Watch fanout, that is output of the FF being loaded with enough current sinks to inhibit operation or make for lousy noise immuunity. Many designs used enough inverters to avoid needing buffers, again a balanacing act. Allison