What is the reason for preferring virgins over non-virgins in Paradise, and does the Prophet's marriage to non-virgins necessitate the superiority of non-virgins over virgins?

The Sharia (definition) did not contradict human nature in inclining towards marriage with virgins. The Prophet (peace be upon him) guided towards this when he said to Jabir: "Why not a virgin whom you fondle and she fondles you?" This is because a virgin is more modest and more attached to her husband, whereas a previously married woman may have had prior relationships. However, marrying a previously married woman may be better in certain cases, as Jabir did due to the needs of his sisters.

As for the women of Paradise, they are virgin houris for the perfection of bliss and pleasure. No human or jinn has touched them, and this is more beloved to the husband.

And His (Allah's) saying: (It may be that his Lord, if he divorces you, will give him instead of you wives better than you, submitting [to Allah], believing, obedient, repenting, worshipping, traveling [for Allah's cause], previously married and virgins) (At-Tahrim/5) indicates that Allah promised His Prophet wives in the best state of righteousness, whether they were previously married or virgins. The precedence of mentioning previously married women does not indicate preference; rather, it may be out of consideration that most of the Prophet's wives were previously married women. And there are great rulings and benefits in marrying previously married women, unlike the marriage of the people of Paradise, which is purely for enjoyment.