If you only saw an image of these glass flower sculptures you would swear that they were real. Even when you do see the maker sitting beside them, you would still have to do a close examination to make sure your eyes weren't playing tricks on you.
Usually, the normal thing to do when trying to recreate the delicateness of a flower is to use materials such as cloth and light papers. While these are nice, they don't hold the permanence of blown glass.
The reason for the gargantuan size of the piece is to make the viewer feel small in comparison. It's about adding a macro element to a typically micro specimen. It also allows for more detail on each petal.