The answer to 'why is my hardwood floor stained' is that there are several common causes for hardwood floor stains, including spills, pet accidents, water damage, and excessive wear and tear. Symptoms may include discoloration, darkening, or a dull appearance in the affected areas.
For minor stains, you may be able to remove them with a hardwood floor cleaner or a DIY solution like vinegar and water. However, for more stubborn or widespread staining, it's best to call in a professional hardwood floor cleaning and refinishing service. They can properly assess the extent of the damage and use specialized techniques to restore your floors.