Why is the alternate static pressure lower than the standard static vent pressure regardless of the venturi effect on both?
A venturi effect pertains to a change in pressure caused by a CHANGE in airflow velocity.  The static air pressure at the static port is not automatically lower just because the air is in motion there. 

After all, the air within the fuselage (and within the piping leading to the static port) is in motion relative to the outside airmass, just as much as the outside airmass is in motion relative to the air inside the fuselage.

However, the overall dynamics of the flow around the fuselage do produce a net drop in pressure inside the fuselage, if it is unsealed.  There must be locations on the fuselage that would be bad places to put a static port because they are the planes where this pressure drop is being created by the overall dynamics of the flow.  

Related answer-- In an unpressurized cabin, why is the cockpit ambient pressure lower than the outside pressure?

Another highly related answer-- Does the pressure at the static ports drop as the aircraft&#39;s speed increases?