Of course, you can eat grass. But this makes no sense, and in some cases, it can lead to not the most pleasant consequences.
Unlike ruminants, which have a special digestive system, including a four-chambered stomach, humans cannot assimilate the nutrients contained in the grass. Therefore, if you eat enough herbs, most likely, you will be nauseous or you will experience diarrhea. At the very least, the grass will just turn out undigested.
In addition, the use of herbs is harmful to human teeth. The grass contains a lot of silica. If you start eating it, the enamel of your teeth will wear off quickly. Goats, sheep, and other ruminants do not have this problem. First, the features of their jaws allow you to grind grass, and secondly, the teeth of such animals are constantly growing, which means that the worn surface of the tooth can be replaced with a new one.
Interestingly, there was a period in history when people could digest grass. That was about 3.5 million years ago. Our distant relatives Australopithecus bahrelghazali had teeth that were well suited for this task.