Saw this oddity last month in Murcia province, Spain. A dedicated bike path that extends for over 30 km and appears to have zero users. It follows the service road of the main RM-1 highway from Murcia city all the way to the coast (just south of Alicante). The service road has almost zero traffic (I passed two cars in 20 km), rendering the bike path completely superfluous, hence its state.
Does it matter what the purpose is? It’s nice to have the option for sport or as a part of a cross country trek.
Nope.