Apart from the economics part of it I do consider giving your dogs human food as a good practice. Not only is the food less expensive but there is also the fact that people try to prepare a balanced diet which would be beneficial to the dogs too. I don't think there are health concerns worth considering here because dogs have more efficient digestive systems as compared to humans , the fact that they can digest comes is a testimony to this. Most families make the mistake of discarding leftovers which the dogs would relish anyday. In any case, this would engender change which is good to their palate. Over time, dogs have developed the omnivorous habit of feeding having learnt to live with with us after the discovery of fire to take advantage of cooked food left by humans in the vicinity of their dwellings. I suppose it also fosters human interaction with the canines because we shape one more aspect of our lives which is very close to our hearts and souls- food.