It's simple because that's cheaper to make.
There is the GUI SynScan Tour handset for people who want more, and it's fairly easily connected to a computer/gamepad/tablet/etc. for those that want to, but I like the simplicity. In fact, there are functions available in SynScan that I don't need.
SynScan is low power, low (red) light, light-weight/one-handed, survives being dropped and has big buttons. Really, once I've finished alignment, the only thing I need is the identity of the next target and the RA/DEC keys.
If I were to add anything to SynScan, it wouldn't be a GUI. I'd add custom tracking modes for comets and, say, the ISS - you'd enter some ephemeris data and SynScan should calculate the rest.