why that might be.

Ultimately, that's the main point of this chapter. Flowers are more important than they might seem at first. They attract animals, encourage pollination, fascinate the human mind, and inspire art. They're specialized to be eaten and spread by certain animals to certain places. A person considering the importance of various plants would be remiss if they didn't give due attention and respect to flowers and, particularly, to the tulip.

One way that Pollan makes the writing interesting is by sharing examples from pop culture and common knowledge.

Pollan makes the secret life of plants and our interaction with them interesting.  One of the ways he does this is by speaking to the everyday reader.  Pollan does not talk down to the reader, but he explains concepts by making them accessible.  A good example of this is his description of a meme in chapter 3.  The subject is intoxication, and the premise moves beyond how plants can be used to alter human consciousness.

A meme is simply a unit of memorable cultural information.  It can be as small as a tune or a metaphor, as big as a philosophy or religious concept.  Hell is a meme; so are the Pythagorean theorem, A Hard Day’s Night, the wheel, Hamlet, pragmatism, harmony …. (Ch. 3, p. 148)

In addition to giving so many examples that every reader should be able to relate to at least one, Pollan reinforces the idea that a meme is something we are already familiar with, even if we don’t know its name.  When he describes memes as “culture’s building blocks,” he helps the reader conceptualize their importance and use.  Useful memes that help us in some way are replicated and considered beautiful or true.  The process of passing on memes is what results in cultural change.  Intoxicants can cause new memes to originate by causing shifts in our thinking along with changes in our consciousness.

Every culture has an intoxicant.  Our love of intoxicants seems to be part of human nature.  It is the reason why it is such a big part of many cultures.  Many of these intoxicants were used in religious rituals, and this is no coincidence.  The transcendence of the human psyche creates the religious experience, and brings deeper meaning to the believer.

Ultimately, Pollan’s description of culture’s effect on intoxication, and vice versa, reminds the reader that intoxication is much more complex than we might have previously thought.  The idea is not that farfetched, since Pollan admits to getting it while high on marijuana!  If that doesn't peak the reader's interest, what will?  It shows that not only does he know what he is talking about, but he is willing to test his theories (and break the law) to prove it.  That definitely keeps the reader turning page after page.  After all, Pollan is not just giving us a lecture on science.  He is telling us a story about human culture, history, and the human psyche.