I would think that most groceries would allow because then people walk out before paying for the food as was the case already. Can't go into McDonalds without paying before eating.

I have always struggled with this concept. I have never been able to accept seeing someone munching on a snack, candy bar or otherwise before paying for it. For me, imjust don't think it is right. But, who am I to judge.

You should not because you have not purchased the item, so it is shoplifting. You may not even buy the item, also shoplifting. It is uncommon that this happens, but it happens.

It isn't yours until you've paid for it, so one should not eat it aforehand.

You have not even paid for the food that you ate, thus the property of the food is still the store's. By doing so, you may be accused of stealing the food.

With prices and taxes changing you might not be sure how much whatever you are snacking on costs, and if you even brought enough for it.

You may have the intention to buy whatever you are snacking on but you may not have enough, and have just stole whatever you were eating.

There isn't really a need to snack in the store before paying. You are not starving to the point where if you don't eat within the next second you'll die, so you can wait.