Luke describes two uses of clothing during Jesus' entry: the disciples place garments on the colt, and people spread garments along the road. Neither action is merely practical.
In an honor-conscious culture, valuable clothing could be used publicly to acknowledge the status of an arriving figure.
Without a prepared saddle, folded outer garments could provide a riding surface. Spreading garments beneath a ruler's path also has biblical precedent: in 2 Kings 9, people place garments beneath Jehu when he is proclaimed king.
The Gospel writers combine such gestures with scriptural imagery surrounding Jesus' arrival. Luke does not require every member of the crowd to have understood the event identically, but the actions visibly elevate Jesus above an ordinary traveler.
The custom helps recover the entry's public force. The crowd is not simply making a road more comfortable; people are using their own possessions to create a path of honor.
Along with the colt and royal acclamation, the garments contribute to a scene in which Jesus enters Jerusalem amid unmistakable signs of kingship, even as the nature of his kingship will soon defy ordinary political expectations.