Why do the Eight Precepts prohibit adorning the body with fragrant flowers and perfume?

This question should be considered from the reverse angle: why do so many people like to adorn their bodies with fragrant flowers and cosmetics? What is the meaning of adorning the body? Why do men and women decorate and dress themselves up? Because sentient beings lack an awakened mind, they do not reflect on or question their own and others' daily behavior; they follow their habitual tendencies and habits, follow all their mental processes, without knowing what kind of mental processes these are. All the mental processes of sentient beings ultimately come down to the view of the body and the view of the mind, which together constitute the view of self (satkāya-dṛṣṭi). Because the view of self is deeply entrenched, it manifests at all times and in all places; there is no intention to conceal it, nor the ability to conceal it, nor the ability to restrain it, and they do not know that it is wrong, that it is a wrong view (mithyā-dṛṣṭi), that it can cause one to fall into the pit of birth-and-death, unable to extricate oneself—even if the Buddha comes to save and draw one out, it is very difficult.

Taking the body as the self is called the view of the body. Sentient beings subconsciously and unconsciously, at all times and in all settings, always attend to their own material form, concerned with how others see them, how others evaluate them, how to make others accept them, like them, and revere them, and thus unconsciously seek to attract the gaze and attention of others. Those who pay great attention to their appearance all do so because of the view of the body; they like to strike poses and preen, their behavior is affected, their smiles are professional, they from time to time fiddle with their hair and hands, dab at their faces, adjust their clothing—myriad small gestures—all revealing a person's view of the body; the feeling of the body cannot be neglected for even a minute, and at no time can they forget the body. One can see how heavy the view of the body is among sentient beings.

If you know what the view of the body is, you can observe whether others have the view of the body and how severe it is, and you will know whether this person has eradicated the view of the body, whether they are a good teacher (kalyāṇamitra), and whether what they teach can lead you to eradicate the view of self and walk toward liberation. Because sentient beings are generally ignorant and unwilling to study the Buddhist sūtras, they lack correct judgment, are easily deceived, mistake the false for the true, and waste enormous amounts of time and energy on wrong paths.

If one does not know what physical and mental state, what physical and mental manifestations, the eradication of the view of self involves, then whether one is a teacher of the Dharma or a listener, one cannot conceal one's view of the body and view of self, nor does one know how to conceal it—one cannot even pretend convincingly. Teachers of the Dharma also know that sentient beings are ignorant and do not understand, so they do not deliberately disguise or conceal themselves; thus it is the foolish guiding the foolish, and no one can climb out of the pit of foolishness. The reason swindlers flourish in the world is that the soil of the world is suitable—suitable for their survival, suitable for their breeding—and the suitable soil is precisely the ignorance of sentient beings. Thus it is the karmic power of sentient beings that summons and attracts the hypocrites.
Now, returning to the main topic: the reason the Buddha established the precepts to restrain the bodily, verbal, and mental actions of sentient beings is so that sentient beings can subdue their incorrect bodily, verbal, and mental actions, subdue their view of the body and view of self, laying the foundation for eradicating the view of self, laying the foundation for seeing the mind and seeing the nature, and also laying the foundation for meditative concentration (samādhi). Therefore, if a person is unwilling to receive and keep the precepts, does not abide by the precepts, then meditative concentration will not arise, they will not subdue their own mind or reduce the view of self, will not eradicate the view of self, and will not see the mind and see the nature.

Those who lack meditative concentration and do not keep the precepts, yet claim to have attained the fruits, seen the mind, and seen the nature—what fruit did they attain, what mind did they see, what nature did they see? So it is not surprising that some who guide others to attain the fruits and to see the mind call upon their followers to comply with afflictions, to abandon the marks of the precepts, and to no longer keep the precepts with marks. This is because their own afflictions are very heavy. To deceive all sentient beings by treating them all as fools is a very unwise move, because the Sahā world is, after all, the Buddha's land, and sentient beings are the Buddha's children; with the Buddha's great compassion, how could He give up caring for and transforming sentient beings, how could He fail to support sentient beings, how could He allow sentient beings to be maliciously deceived?