Because I don't see any "huge" risks. The risk of abduction is incredibly low. I would have to gauge the relative risk of fire in each location, but in a hotel room away from the kitchen, then I am happy if I have a working smoke alarm. The risk of SIDS is ever present, but we always opt for non-smoking rooms and follow the usual guidelines (and again our presence does nothing to prevent this).
The main risk imo is what might happen if the children wake up. Firstly we know our children well, and they are both sound sleepers. If they are ill for example we take a different view of the risk of leaving them. Secondly we always prepare them for what we are going to be doing so they know where we are, and also that there will be someone listening out for them. They know how to get hold of us in an emergency. Thirdly, we mitigate the risks of them hurting themselves in their room (so they can't wander out on balconies, there is nothing that can give off heat etc).
There are a host of other things that we consider, but would be too long to list - the location of the hotel, the type of clientele in the hotel etc. We wouldn't necessarily make the same decision each time. And when our second child was still small and in a cot we would always have a babysitter as we didn't feel it would be fair for the baby to wake his older toddler brother and for his brother to have to deal with that.
If I felt that concerned about the risk of abduction, then frankly I wouldn't go on holiday to that location in the first place.
The above summarises my views, but I wouldn't expect every parent to have the same view. Some children are sleepwalkers, some are generally poorly, some would be devastated and traumatised if they woke and foudn their parents not there. All those factors would be considered by the parents and they may make different views.
We're talking about having dinner in the hotel dining room here - not taking a taxi across town.
"ok i'm going to ask it, when so many other risks are frowned upon why is it acceptable to leave sleeping children alone or at least not be acceptable to frown upon it or question the reasoning behind it? "
Well I tried my best to give you my reasoning for it. I don't actually see it as something I would necessarily judge someone on, as I suspect a lot of decision is down to where you are at the time and what the location is like etc. As I have already stated on this thread, I looked at the resort that the McCann's stayed at and decided that it wasn't suitable for us as the restaurant was too far from the rooms and there was no listening service (and I'm not keen on a night creche). But if I am in a suitable hotel and resort and wanted to have dinner then yes, I would leave my children if I was happy with my own assessment of the risks.