Why always seven? WHY!?
Maybe because when many of us hear "random number" it equates to "unusual number". Well, one is just one, there's nothing unusual about that. 2, 4, 6, 8, 10, even numbers. Three is too low, and nine is too high... And five is exactly half of ten which is the basis of our number system. Process of elimination leaves seven.
...Any logic here? xD