The wisdom in wearing the two garments of iḥrām

Answer: What occurs to me is that the wisdom in forbidding the muḥrim from wearing stitched garments and in obligating him to wear the cloak and waist-wrap—garments devoid of adornment—is:
1. Manifesting humility and destitution: when the muḥrim dons the two garments of iḥrām, he is diminished in his own sight and in the sight of onlookers; the onlooker, when he looks upon those in iḥrām, does not distinguish between great and small, nor between master and subject, etc.
2. Restraining the soul from pretension, self-aggrandizement, and arrogance; for in that attire is what turns the soul back from its caprice and from aspiring to its desires.
3. The muḥrim’s soul is too humbled to boast as the people of Jāhiliyyah used to do—they prided themselves and recounted the glories of forefathers and descendants and exaggerated in mentioning exploits and virtues, etc.
4. In prohibiting perfume for the muḥrim there is the completion of manifesting humility and destitution and the feeling thereof; for when the muḥrim is in that simple attire and the odors of sweat and grime emanate from him, his humility and destitution are increased. In the report describing pilgrims, they are “disheveled and dusty-smelling (al-shuʿth al-tafal) (1).”
5. Perfume is among the things that help stir desire toward women; prohibiting it for the muḥrim distances his soul from desire for women and severs its causes, so that the pilgrim may devote himself to the worship of his Lord.
Here, He, Exalted is He, said: “So there is to be no sexual relations and no disobedience and no disputing during Ḥajj.” [al-Baqarah:197]. And the Sunnah has come with the prohibition of concluding a marriage contract for one in iḥrām.
6. Intercourse with women is prohibited because of the preoccupation it causes, diverting from performing the rites of Ḥajj as they ought to be performed; by prohibiting women, the muḥrim’s heart turns to the remembrance of Allah and the performance of the obligations of his Ḥajj or ʿUmrah.
7. It may also be said: the gathering of pilgrims—all in that modest white attire, disheveled and dusty—reminds one of their gathering for judgment; for they will be resurrected in a like state.
Yes, benefits follow from what we have mentioned of wisdoms and secrets—foremost among them restraining the soul from self-aggrandizement and arrogance, and strengthening the motives of humility and lowliness; and that is among the greatest causes of mutual affection, mercy, and brotherhood.
8. Muslims gather from every place for Ḥajj and ʿUmrah in that attire through which the distinctions among them are effaced: no superiority of one nation over another, nor of one people over another, nor tribe over tribe, nor person over person—no, and no, etc.
Instead, brotherhood appears among them and unity in servitude to Allah Most High, and in His obedience and magnification, and in complying with His command to gather at ʿArafāt, then depart from it all at once, then spend the night together at Muzdalifah and remember Allah there, then depart from it at dawn to Minā to stone the Major Jamrah, then … then … and so on.
All of that reminds the Muslim and instills within him that Muslims—though their lands be far apart, and tongues and hair and lineages and complexions differ—are nonetheless brothers, one community: not divided by the remoteness of regions, nor by racial impulses, nor by the features of complexions and hair, nor by differing languages. What unites them is Islam and its laws, and servitude to the Lord of the Worlds.

(1)- Tafal: his odor has altered; it is said: “So-and-so became tafal”—he left off perfume and his odor changed, so he is tafal. Also said of the masculine and feminine: mutafāl. (al-Muʿjam al-Wasīṭ)

Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.1