Squirrels are cute. People like cute things. They also like friendly things, which squirrels have also got in spades. People tend to keep them in places they can be seen easily like parks or college campuses, which is great and the world is better for it. Yet, when you try and go up to them without food, they run away like crazy. I resented this about them for a while. Then I thought about how they must see us.
Keep some facts in mind. A fast human when running at a top speed can run 10 miles while a normal squirrel can normally run 20 miles per hour. We also lumber over them and our feet are larger than their easily crushable little bodies. That is the world they live in. Think of humans lives. Picture skyscrapers all sudden came to life and started to lumber around until they saw you and would start runtowards you in hope of petting you, this is the life squirrels lead every day. And this is most likely why they run away when you try and pet them. Well, unless you have food.