Question

If you can simply pour sand into a cup then why is it not a liquid?

Answer 1

If you pour sand into a cup(empty) why would it change? 
If it had water in it then the sand will sink to the bottom, and not change forms.

Answer 2

If you, for example, poured it onto a wide cup with a volume equal to the total volume of the sand particles, the sand would not spread out to fill the container but would bunch up together in the middle.