Possibly this is IMHO.
Doper parents/psychologists: when you are raising your children, do you place more emphasis on morality (Playing with matches is wrong), or on your child’s self-interest (If you play with matches, you could start a fire and burn yourself.)
Should both be focused on equally? Does it depend on the child?
Should some issues be moral issues and others pragmatism issues? Which ones?
Ask me when she’s old enough to be playing with matches. 
For the example given, we’d probably use “you could hurt yourself” line as it really isn’t a moral issue.
My daughter’s only three, but we usually try to explain natural consequenses rather than preach “right and wrong.”
Both have their place, but one should consider what the child is old enough to assimilate.
Trying to explain morality – or even empathy – to a two year old will get you nowhere. Showing her what happens to an object when it catches FIRE, now… THAT gets results!
It depends. I suppose you could frame the matches issue as a morality issue by telling a kid not to play with matches in case they start a fire which hurts other people. Certainly my kids are aware of the danger of bushfire and how wrong it is that the majority of our bad recent fires were set by arsonists.
But on a day to day basis, I’m more inclined to say Don’t play with matches, you’ll get hurt.
When they are young they do not have the processing ability to understand “You’ll get hurt”, so simply saying “NO!” is enough. But by age 2 they start asking “Why?” to everything, and you have to provide them with an answer.
They will not understand a complex answer- they need something they can relate to simply, ie “You’ll get an owie”.
IMO, it’s not until they are 4-5 that they can grasp the consequences of their behaviour. At that point you can explain what could happen.
I don’t think explaining the possible outcomes is necessarily a moral issue, especially in the example you provided. Fire can be bad. A match can set a house on fire. It can kill. But “kill” is not a tangible concept in kids’ minds (other than what they see on TV or in games).
Were it an issue such as using alcohol, smoking, sex at a young age, then yes parents DO tend to interject their moral beliefs into their objection, and rightly so. Those are choices that have slow long term effects on them rather than the immediate “OW!” of a burn.
“Don’t hit your sister” would probably be an early one they can grasp. It hurts your sister, she’ll cry, she’ll be very sad…That’s Not Nice. At two, Not Nice probably means that it makes Mom & Dad angry. At three I think they were catching on that we had standards for behavior, things that are “nice” and “not nice”…because we said so. Then at 4 or so (the why era) we got into further explanations of why certain behavior is right or wrong.
For playing with matches, I think we used both: you could hurt yourself badly or hurt someone else if you start a fire…It’s Very Dangerous. Again, first that means it makes us mad, later they understand other consequences. Whether or not they can understand it all though, they hear it. So I guess we do focus on them equally.