I love this question. My first experience with science was astronomy. I remember bugging my dad about space and the universe when I was 5. It is true that there is estimated to be more stars in the universe than all the grains of sand on all the beaches in the world. Hundreds of trillions, upon trillions, upon trillions of them. However we cannot see all of these stars from the ground when we look up at the sky. The amount of stars we see varies with altitude, weather and geographic location. Go to Antarctica, fly at 30km altitude and you will see many more stars than someone in Shanghai looking up at the stars on the street.
Yes there are more stars in the sky than grains of sand on the beach. The problem is we cannot see them all. Pollution is a big factor, as is the fact that many stars are too dim to be seen with the naked eye. In theory if we had a sensitive enough retina and no atmosphere, starlight would make the sky almost opaque.
Of course if there is no one to see the stars, some scientists argue that the stars would not exist. There is a theory that our universe cannot be separated from human consciousness. We know that when we do the double slit experiment with the electron, which slit it comes through depends on how we observe the experiment! Wow! Reality and our perception of reality cannot really be distinguished. The paradox of Schrodinger's cat is another example of this. In fact you could argue that if we all perceive the universe differently, our universe is really a multiverse of different frames of human perception.