But keep in mind, the late St Sheldon Brown had the best of both worlds with a fixed 3-speed!
Having choices is a wise decision, just fixed is kinda not pleasant for anyone who just wants to simply pootle around or commute, it's taste that's not for everyone. For getting more people to ride over using the air-con tin can, the experience of riding downhill fixed, even on a moderate descent, could put them off completely.
Hub gearing, like fixed gear also has it's advantages in being relatively easy to maintain over external derailleur set-ups and is great in crappy weather conditions. Simple to see why hub gears developed in the UK, while the French developed external derailleurs for drier conditions. With fixed there's always the option of a flip-flop hub and having a single speed with freewheel if you want that flexibility.
I scored a box of Sturmey Archer hubs with the amazing Raleigh carrier bike a few week back at the Vintage Cycles swap meet at Abbotsford Cycles. Hours, if not weeks of grubby bike nerdy fiddling fun awaits! (alongside a bit of swearing & the occasional profound curse!)
Although admitting to one's bias, as I'm just loving the Alfine hub on the Kitten of Doom uber commuter, and The Blokes built up a Rohloff Speedhub on a On-One frame for off-road.