The more you leave a bowl lying around with food in it, the less chance you will ever have of establishing set meal times, where they know to eat what is given to them.
If they know they can simply 'graze' all day at their leasure, they will learn to turn their noses up at food until somthing better comes along, as they know it's always available.
Set meal times for dogs are very important to me in establishing good eating habits for the future.
I know a lot of ppl just leave a bowl of kibble out 24/7, but that's not my idea of good eating routine. I don't 'graze' all day, as I don't think that's healthy for me, either! Lol.