Well, in reality, we will never know 100% because we can't ask them but it is important to know that grazing on grass is a very normal canine behaviour when they're not sick, some dogs really seem to enjoy certain grasses especially new sprouts.
🌱 They like the taste
🌱 They are self selecting foods that they need and may need this addressed with the food you feed them, it might be lacking
🌱 They are trying to settle an upset tummy, dogs eating grass because they'll ill is said to be less than 25% of grass eating cases
🌱 A learned behaviour from other dogs
🌱 They're hungry i.e. on a diet
🌱 A 2009 study found that the puppies were more likely to eat grass if their Mothers did whilst nursing.
If you suspect grass eating may be nutritional, you can try feeding foods high in chlorophyll such as: spinach, collard greens, chlorophyll, spirulina, alfalfa, broccoli & parsley.
If your dog is eating grass regularly which results in them throwing up, head to your Vets.
Eating grass is considered safe but be sure you only allow your dog to eat grass from areas that chemicals haven't been used on.