Light has it covered. A vacuum doesn't suck. It just removes any pressure that would try to cancel any other pressure.
Pressure is caused the air molecules moving and banging against other molecules. If air molecules bang against a wall with no molecules banging against the other side, the wall will be urged to move and there will be nothing to stop it.
If there are half as many bangers on the other side, the wall will have a full urge to move one way, but a half an urge to move the other way. The wall will be urged to move, but with with less urgency.
If there are as many bangings happening on one side as the other, the wall be in equillibrium, with no need to try to go one way or the other.
Atmospheric pressure is caused by gravity sucking air molecules downward. At the bottom of the pile the total weight of molecules bearing down upon a certain point, or, area, can be measured as pressure.
Inside a Space Pipe, if there are absolutely no molecules, there will be no absolute pressure, because there are no molecules to do any banging. If there are any molecules, they will be sucked down by gravity and at the bottom of the Pipe there will be some weight of molecules which can be measured as pressure.
In the Space Pipe, if there are no molecules, there will be nothing to resist the banging of atmospheric molecules. However, since there is nothing there, in the pipe, there is also nothing that can do any work of lifting or "sucking" up. Nothin' cain't do nothin'.
In a vacuum, there is no physical body which can push or pull upon any other body. In a gas, such as the atmosphere, there are molecular bodies which can move and push ( but not really pull ) against other bodies.
Since I am easily amused, it has entertained me that the measure of pressure in inches of mercury is ( very roughly ) the same as feet of water.