Well, I'm sure it has something to do with photosynthesis.
But I'm talking about symbolically, or "figuratively speaking".
"Literally speaking" means to view something only for what it is. For example, the flowers face the sun because they need the sun for photosynthesis, which is how they make their own food. So "literally speaking," flowers face the sun for photosynthesis.
"Figuratively speaking," however, is to speak of something in the figure of what it means. A figure or symbol of flowers might be people. And the sun that the flowers (people) are facing might figuratively, or symbolically, represent the light of knowledge, or truth, or true beauty, or Divine Knowledge, or God Himself.
So, figuratively speaking, why might people be equated with flowers, and why are they always facing the sun?
If you were expecting the figurative answer, well, you'll have to dig deep and find the answer for yourself.
(figuratively speaking, "dig deep" means to think about it very hard.)
To speak figuratively is to make an analogy or comparason.
figuratively speaking = symbolism = making an analogy = making a comparison (IT'S ALL THE SAME)
dig deep = search deep in ones mind = think hard