While I agree in order to have the highest success rate with animals in captivity means merely replicating their natural environment is often not enough I disagree with your point. See you need to look at it from a view point which includes no anthropomorphic views what so ever. What you're not considering is that I (for instance) was stating average winter minimum temperatures taken over decades that these animals have evolved to handle. While yes some would die because they are not strong enough to survive it is likely this wouldn't be because it was simply too cold, more likely there would be a deformity or issue which prevented it from gaining enough condition before the cold set in. Remember these animals have evolved for THOUSANDS of years.
So if these animals are exposed to temperates of <5 C on a regular basis and are restricted to hiding under a fallen log then your bearded dragon kept inside, often in a wooden enclosure that has a hot spot of 40-50 C during the day and an ambient temperature of 25 C, has hides provided within the cage which is kept in an INSULATED house should have no worries handling whatever temperature winter can throw at it considering almost every house will have some form of heating during winter and even those who don't are unlikely to ever get much below 10 C.
So no providing heating overnight is not going to harm them but in a lot of cases it isn't neccessary and is a cost some people would not be able to justify.
I am talking about CENTRALS here, which while slightly off topic is still relevent to the direction the thread has headed.
