Spokes work hard!!!
They spend their lives under extreme tensile forces and are repeatedly shocked with the impacts from off-road riding. All the while we cover them in mud/sand before jet washing them with high pressure water and then repeating the process.
Spokes wear out. It is not a question of 'If' but 'When.'
At SPIN I hold many common size spokes in stock, while others are generally on next day delivery to me. Custom made spokes are also available. There hasn't been a wheel yet I have not been able to supply spokes for.