It's a matter of definition really.
'Juice' is generally considered liquid extracted from fruits/veggies. A "juicer" separates all the fiber and pulp from the liquid of the fruits/veggies. The resulting liquid is juice.
Blenders do not remove anything. They simply blend the entirety of fruits/veggies put in the container into a smooth consistency - this is a smoothie: all the liquid plus all the blended fiber/pulp together.
You can make "juice" with your blender by making a smoothie and straining it to remove the fiber (by using a nut bag fro example).
I hope that answers you question.