Hardwood can look dramatically worn while still having years of useful life. Scratches, a dull finish, and an outdated stain often point toward refinishing rather than replacement.
Replacement becomes more likely when boards are severely water-damaged, the floor moves widely, or the wood has already been sanded too many times.
A professional inspection should look beyond the surface. Board thickness, subfloor condition, damaged areas, transitions, and desired color all affect the recommendation.