Everyone needs water. While people can get water on their own, cats rely on getting water from their owners or from random water sources (ie. the toilet). So it’s best to keep your cat hydrated to minimize the risk of kidney disease, constipation, and urinary tract disease.
One way is to offer standing and running water so your cat can choose. Also put the water separate from the food bowl to give them a choice of which water supply they want. Finally, consider offering canned food along with dried since canned food provides extra moisture as well. The more hydrated your cat, the more likely it will be around longer to keep you happy.