The act of putting water around the plate

As we know water acts as a repellent to many tiny creatures that roam on the floor seen and unseen, hence the circle of water stops them to approach the plate when kept on the floor also they are attracted towards the part of food kept outside the plate making it safe to consume the food. This practice is redundant while eating on dining table which is presumable cleaner than the floor. Those who still practice it on table are just following tradition without knowing the meaning behind it.