The structural factors that keep this book selling appear to be its dual-audience design, which establishes it as a perpetual gift vehicle, and a narrative that models its own intergenerational transfer.

Its core differentiation from other picture books is that its primary emotional consumer is the adult, not the child. While most books in the category become obsolete as a child ages, this one's relevance is tied to the parent's life stage, making its appeal evergreen. The mechanism that keeps it selling, therefore, is its function as a ritual object. It is perpetually purchased not for a child's library, but as a symbolic gift for baby showers, graduations, and Mother’s Day, creating a self-renewing sales cycle driven by life milestones.

This focus on the universal, almost archetypal, parent-child bond grants the book resilience to era shifts. The core themes of time, love, and the cycle of life are insulated from changing trends in illustration, humor, or educational philosophy that can make other books feel dated.