Because of your tear duct get tired as the rest of your body. When it happens, they produce less fluid, which dries out your eyes. It stimulates the tear ducts when you rub your eyes, and spread moisture over your eyes. It also has effect on ocular muscles, you are also putting pressure on your vagas nerve. It could reduce blood pressure, lower the heart rate and relaxing the whole body.
You know the right way to treat your eyes will be eyes massage other than crucial rub. You must keep hands clean when you do this as well. Why people feel good, because it can relief the visual fatigue even prevent it from myopia, and increase the circulation of eyes blood, relief the eyes bad etc. Once again, I must say you need massage your eyes in a right way other than rub, Ok? If not, it will damage your eyes even get it injured, because eyes muscles are subtle.
After working for a period of long time, people will feel tired, and especially the people working in office, their eyes will feel very dry so that they can not focus on working any more, and if you have the same issue, I suggest that you'd better stop working and have a little rest, and you can rub your eyes or look the distance scenery to make you feel better, and this triggers a reduction in blood pressure, which helps you relax and get ready for working again.
Well, of course it will make you feel good when you rub your tired eyes. Because in everyday life, we just have to open our eyes to look at things and some people who have a job which are associated with the computer are even worse. They make their eyes too pressed. When you rub your eyes, just you have massage for your body; it will improve the blood flow. In this way, your eyes nerve can be relaxed so in the end your eyes and even your body will feel comfortable. But on the other hand, to make your eyes healthy, you should not overuse your eyes and make sure to have a good rest.