The Buddists always give the lotuses to the monks or to the temple. They do as tradition. In fact, they can give any kind of flower to the monk. Monks are from various kinds of people with various of status. There is no classes or levels after ordination. Every monk respects each other. Buddha said that the monks were from many different places, so people can give them any kind of flowers.
Why do people give lotus to the monk?
Buddha compared human as lotus in 4 position. First is the under-the-mud lotus. That is people who cannot understand anything, although the genius tries to teach them. Second is the under-the-water lotus. That is people who must take time to understand something. Third is the boom lotus. That is people who can understand anything so fast, and they really need the teacher or the knowledge from anywhere. Forth is the bloom lotus. That is people who are really bright. They can understand everything suddenly and exactly correct.
Surely, the lotus that people can pick up from the water is the third or the forth. They think that monk must be bright people, because they are calm. When people are calm, they will understand everything well.
This is the reason that Buddists give monk the lotus.