The speaker questions why the young man, who possesses true natural beauty, should live in a corrupt world where counterfeit beauty imitates him and nature itself has become depleted and bankrupt of genuine vitality.
The volta introduces a brilliant inversion: the speaker moves from asking why the young man should tolerate a corrupt world to suggesting that nature itself is now bankrupt, dependent on the young man's vitality to survive. Nature 'hath no exchequer now but his'—the young man has become not just beautiful but functionally necessary, a kind of last treasury from which nature draws remaining resources. The personification of nature as 'she' creates a maternal figure now impoverished and desperate. What was once assumed as nature's infinite fecundity is revealed as depleted. The young man's beauty is thus positioned as a relic of an earlier, golden age. He represents nature's lost abundance, a walking museum of what beauty once was.
The first quatrain's obsession with false painting and stolen beauty contrasts with the later revelation that even this fakery depends on authentic beauty to imitate. False beauty cannot create; it can only copy. The 'poor beauty' that 'indirectly seek[s] / Roses of shadow' is parasitic on genuine roses. This hierarchy—authentic beauty above, false beauty below—is structured into the very language of the poem. Yet the sonnet also suggests a historical degradation: there was an age when beauty was abundant and authentic; now it is singular and precious, hunted and imitated. The young man represents not eternal beauty but the last remnant of a lost era of authenticity.
Like seeing someone genuinely beautiful and talented in an era of filters, plastic surgery, and fakeness. You wish they could live in an age that valued real beauty, not this artificial version. Instead, fake people are copying their real thing.