the water in the lifted straw is not putting any pressure on the water in the glass.
it cant fall because of the vacuum at the top of the straw.
this same scenario occurs in larger pipes.
take a 2" pipe 8 ft long and put a cap on one end.
then submerge it in your swimming pool , then lift it straight up
with the capped end pointing upwards.
the water will stay in the pipe until you completely pull the pipe out of the water.
ie...when the air can rise into the pipe.
if you hold your hand directly under the lifted pipe you will not feel any pressure from the water in the pipe.
untill air can rise up and allow the water to fall by removing the vacume in the pipe.
or use a 2 liter coke bottle , fill it with water then
turn it upside down in a coffee cup , as soon as the water in the cup fills up and touches the top of the coke bottle
the water will stop comming out.
just like a pet waterer , the pet drinks water , the water level falls , air moves up into the tank , water falls down again.
the water is held up by the vacume.