Why is Friday singled out for great importance?

Allah, chose Friday to be the best of days before Him, and He singled it out for major events and great qualities, which are the reason why Muslims are obliged to venerate this day and take it as one of their Eids or festivals in which Allah has prescribed rituals that He has not prescribed for other days.
Moreover, Friday prayer has a particular virtue and great qualities through the blessing of this great day.
Ibn al-Qayyim (may Allah have mercy on him) said:
Friday prayer is singled out from among all the other obligatory prayers for having particular characteristics that are not found in other prayers, including the fact that it is offered in congregation, has a minimum number of worshippers required in order for it to be valid, the iqaamah is a condition of its being valid, one must not be travelling in order for it to be obligatory, and the recitation is done out loud.
There is an emphasis on its importance the like of which is not mentioned for other prayers except Asr prayer.
The Prophet’s Sunnah also singles out Friday prayer by encouraging believers to do ghusl for it and to use perfume (for men only). It is also strongly encouraged to come early for the prayer and there is a great deal of reward for walking to the prayer. Concerning these special characteristics, Saâeed ibn Mansoor narrated from Naâeem ibn Abdullah al-Mujammir that Umar ibn al-Khattab issued instructions that the mosque of Madinah be perfumed with incense every Friday at midday.
The main reason for venerating Friday prayer is because of the divine decree that singled out this prayer and this day for special virtues. This is one of the manifestations of Allahâs Lordship as He alone singles out for veneration whatever He Wills of His creation and whatever times and places He chooses. He is the One Who does whatever He wills for reasons that He, may He be glorified, knows.
If you ponder this creation, you will realize that this choosing and singling out are proof of His Lordship and Oneness, and of the perfection of His wisdom, knowledge and might; that He is Allah, besides Whom there is no other god, and He has no partner who can create as He creates, or choose as He chooses, or control as He controls. This choice, control and singling out, the effects of which are evident in this world, are among the greatest signs of His Lordship and the greatest testimony to His Oneness, the perfection of His attributes and the truthfulness of His Messengers.
Al-Allaamah Ibn al-Qayyim also stated that this singling out and choice are indicative of the inherent virtue of the thing chosen, for which Allah blessed this time. By His knowledge and wisdom, Allah may grant to a certain place, time or person that which qualifies it to be chosen by Allah and favoured above others.
He said: This concept may not be understood by the one who regards all individuals, deeds, times and places as equal, and claims that there is nothing inherent that makes one thing better than another, and that precedence is given to some things over others for no reason. This view is invalid for more than forty reasons that I have listed elsewhere. It is sufficient, in order to understand the falseness of this view and how corrupt it is, to note that Allah, may He be glorified and exalted, refuted this false view when He said: Allah knows best with whom to place His Message which means: not everyone is qualified or fit to convey His Message; rather the Message has those who are suited to conveying it and it cannot befit any but these people; Allah knows better than you who these people are. If all individuals were equal — as these people claim — there could have been no argument against them in this verse.
Similarly, Allah says: And when there comes to them a sign (from Allah) they say: We shall not believe until we receive the like of that which the Messengers of Allah had received. Allah knows best with whom to place
What is meant is: Allah knows best who will give thanks for His blessings, so He singles them out for His bounty from among those who will not be grateful to Him. Not everyone is fit to thank Him or to receive His blessings and be singled out for this honour. Those individuals and places and so on that Allah chooses have some inherent qualities that are not found in other people and places, and it is for that reason that Allah chose them, gave them precedence because of those virtues and selected them. This is His creation and His choice.
Allah does not choose anything and give it precedence except for a reason that led to it being singled out and given precedence. Yes, He is the One Who created this reason, as He is the One Who created it then chose it after creating it.
To sum up, all the characteristics of this great prayer are by the grace of Allah, may He be glorified and exalted, to His slaves. He chose it by His decree and singled it out for His bounty and blessings, thus it attained this great importance in this world and in the Hereafter.