Yeah, me too. When I started the 2.X series I thought that themes will be really needed and somewhat relevant. Several themes came to 2.X so I thought that for 3.X it will be the same thing.
I don't know if it is that the default theme just fit great or something else but I rarely notice people asking about themes or about how to make them.
At this time I'm keep adding configurable settings for theme like tone, top bar color, etc. That seems to suit 99% of the needs but if someone want to do several editing I'm always open to help and provide assistance.