It’s definitely not an asset. It’s near practically a consumable. It will degrade with use, and over time. It will not maintain it’s current value, let alone increase in value.
All physical assets degrade with use and only a very few increase in value in real terms.
Counterexample: guitars improve with use and age, not degrade.
Every part that the player or strings regularly touch will wear with use and eventually need to be replaced or repaired.
Strings are not the asset, they are a consumable. Many store guitars long term without strings to avoid unnecessary additional neck tension.