It might be "just the way things are" with small Fiats, although logic dictates that it would be easy to resolve on the 500 simply by fitting the appropriate part(s) from the driver's side of a LHD vehicle. If it is "just" a software issue then obviously that is not going to be possible.
However most of the cars I have owned have had one-touch on all electric windows: 1990 Vauxhall Cavalier (front only), 1990 Vauxhall Astra (front only), 1993 Cavalier (front only), 1995 Cavalier (all), 2002 Ford Mondeo (all), 2002 Vauxhall Zafira (front only) and 2007 Ford S-Max (all).
I had a 1997 Peugeot 406 where only the driver's window was one-touch and the switch was obviously different (clearly marked with an "A"), I also had a 1999 Peugeot 306 for a short while which I think had one-touch on both sides but I can't remember for sure!
I hear what people are saying with regard to cost but I don't think this particular issue is to do with cost at all, I think it's probably some misguided "safety feature". With regard to the boot light, the wiring is almost certainly there with just the lamp itself missing as there would probably be more cost involved in varying the loom although there is obviously a saving by not fitting the lamp unit.