What is the wisdom behind urging against marrying bondwomen and preferring patience over it, even though Islam honored "slaves" and reduced slavery, and these women need protection and chastity?

It is not permissible for a free man to marry a slave woman except when fearing falling into sin (haram) and not having the dowry for a free woman. The wisdom behind this is to prevent his children from becoming enslaved, as indicated by the noble verse: "And whoever among you cannot afford to marry free, believing women, then [he may marry] from among those whom your right hands possess of believing slave girls." (Quran 4:25) And it is better to be patient and abstain from such a marriage.