I'd say it is a matter of emotional attachment, those animals that we consider pets/companions we tend not to eat. One way of seeing if that opinion holds water would be to see if in societies that do eat dogs if they also have dogs as pets/companions and if they do, do they eat those pet dogs?
Even if the above does hold some water I don't think it says anything really about the underlying "why" as we also know of societies in which the opposite is true - they at least eat a symbolic portion because of that attachment. And many farmers can be fond of their animals but still are fine with them being slaughtered.
In the end I do think the reason is simply "tradition" - what we are brought up to consider the norm is the norm. That doesn't mean it is logically coherent or anything like that but such behavioural traits are part of human social behaviour. Sometimes trying to look for a "reason" requires us to remember that we are not rational creatures, we are irrational creatures that have learnt some clever tricks such as logic to help us survive!
Even if the above does hold some water I don't think it says anything really about the underlying "why" as we also know of societies in which the opposite is true - they at least eat a symbolic portion because of that attachment. And many farmers can be fond of their animals but still are fine with them being slaughtered.
In the end I do think the reason is simply "tradition" - what we are brought up to consider the norm is the norm. That doesn't mean it is logically coherent or anything like that but such behavioural traits are part of human social behaviour. Sometimes trying to look for a "reason" requires us to remember that we are not rational creatures, we are irrational creatures that have learnt some clever tricks such as logic to help us survive!