SB 12.3.14

kathā imās te kathitā mahīyasāṁ
 vitāya lokeṣu yaśaḥ pareyuṣām
vijñāna-vairāgya-vivakṣayā vibho
 vaco-vibhūtīr na tu pāramārthyam
kathāḥ — the narrations; imāḥ — these; te — unto you; kathitāḥ — have been spoken; mahīyasām — of great kings; vitāya — spreading; lokeṣu — throughout all the worlds; yaśaḥ — their fame; pareyuṣām — who have departed; vijñāna — transcendental knowledge; vairāgya — and renunciation; vivakṣayā — with the desire for teaching; vibho — O mighty Parīkṣit; vacaḥ — of words; vibhūtīḥ — the decoration; na — not; tu — but; pārama-arthyam — of the most essential purport.
Śukadeva Gosvāmī said: O mighty Parīkṣit, I have related to you the narrations of all these great kings, who spread their fame throughout the world and then departed. My real purpose was to teach transcendental knowledge and renunciation. Stories of kings lend power and opulence to these narrations but do not in themselves constitute the ultimate aspect of knowledge.

Since all the narrations of Śrīmad-Bhāgavatam bring the reader to the perfection of transcendental knowledge, they all give supreme spiritual lessons though apparently dealing with kings or other mundane subject matter. In relation with Kṛṣṇa, all ordinary topics become transcendental narrations, with the power to bring the reader to the perfection of life.