Example of tectonic plates: Plates can move at about 2.5 cm per year, about the speed that your fingernail grows. Apart from the sudden movements that we feel during earthquakes, it is difficult to feel the continents move because we are moving at the same slow velocity as the continents. It is similar to being inside a car moving at 120 km
Same reason we are stable on earth - because we are all moving together so, we(the earth and people) are stable and still relative to each other this is similar to being in a car with someone, racing 60 mph down the expressway the passenger and the driver appear to be not moving, relative to each other