They May Enjoy It
Though it may not seem too likely, there also lies a slight chance that your dog might actually like this activity. Maybe they might love to chew on the fresh grasses or the new forming fresh springs. It might enjoy the taste and snack on it.
Genetics
The dogs were not inherently domesticated beings. Though thousands of years of domestication might have evolved their physiology, they have that genetic factor ingrained in them. The early dogs hunted and fend for themselves. During the course, feeding on grass was a source of additional nourishment. Thus, if your dogs eat grass, it is an act that is performed by his nature.
Why You Should Worry
Though the act itself is not very harmful until practiced in excess, it is not healthy for the dogs. The grasses are a source of parasites that might be already there or picked up from the waste (especially the fecal waste of other animals). This might get your dogs to get infected and get sick too.
Another source of danger might be the chemical fertilizers and pesticides sprayed for the plants’ growth. These chemicals are hazardous and, when ingested, might harm pets. Lastly, the plants might be dangerous themselves. Some plants are toxic by their very nature. The animals generally have their way about things and get to know what to eat and whatnot. Sometimes this might not work as effectively. Hence it is a requirement that you should never keep plants that are toxic in your home if you raise a dog.
What Can You Do?
If the habit is because of improper diet, then you should consider adding foods that will cater to their nourishment needs. You can consult with a veterinarian and look for what you should include more. If the habit is self-medication for an upset stomach, you should not worry about it. But then look into reasons why the dog might have had an upset stomach. For the stress-eating ones, try to distract them with other things. Like giving them a chewing toy would suffix their craving a little. Spend more quality time with your pets and ensure they do not feel left alone.
Conclusion
Eating in a small amount is fine, but excessively might attract undesirable effects. Hence, keep an eye on the dogs. Make sure they do not cultivate this as a habit. You can train them or distract them by preventing them from eating grass.