The crux of the matter is sexual purity—whether one attains sexual fulfillment through marriage or abstains from sexual relationships by virtue of one's gift of celibacy.
Not everyone has the gift of celibacy, like the apostle Paul. For most, marriage is the norm as we are wired that way.
Elsewhere, in Hebrews 13:4, we read:
'Safe sex' is not just about putting on a protective sheath. To be safe from God's judgment, we have to follow His laws.