Internal hubs are common in places where biking is common - ie. Amsterdam.
Derailleur's just seem to be far cheaper, I suspect because most of their parts can be made from stamped steel, whereas most parts of an internal gearbox must be CNC machined and face hardened.
Deraillers are a bit more efficient (almost no loss) and overall simpler to work on. They also (generally) offer a wider range of geear ratios.
Internal hubs work great, but have a bit more loss, tend to weigh more, and when they start going sideways tend to go really wrong. But for the commuter-y / daily use like what you mention they tend to last and be more weather resistant.
Because of all of this they haven't found a place in much hobby/fitness mountain or road biking, but are really great for less hilly utilitarian needs.
Derailleurs have, on average, 2% lower loss than hub gears, when new.
However, many suggest that because hub gears usually have an enclosed chain, whereas derailleurs rarely have an enclosed chain, that 2% is usually eclipsed by chain losses as the chain gets dirty/rusty/worn far faster on derailleurs.
Only the expensive ones have the range and you can buy a complete entry level bike for the price of a decent one. They are still heavy and have more than noticeable drag.
Derailleur's just seem to be far cheaper, I suspect because most of their parts can be made from stamped steel, whereas most parts of an internal gearbox must be CNC machined and face hardened.