You should stain your deck to protect it from the elements, prevent wood rot and insect damage, maintain its appearance by highlighting the wood grain, and extend its lifespan by shielding it from moisture and UV rays, which can cause warping, cracking, and fading; in essence, staining acts as a protective barrier that keeps your deck looking good and functioning properly for a longer period of time.
Key advantages of staining a deck:

• Moisture resistance: The stain keeps water from seeping deep into the wood, lowering the risk of mold, mildew, and decay.
• UV protection: Prevents sun damage, which causes wood to fade and decay.
• Improved aesthetics: Stain highlights the natural beauty of the wood’s texture and color.
• Pest control: A professionally stained deck is less prone to pest infestation.
• Staining can help protect your deck’s structural integrity by minimizing moisture absorption.