A combination of art and a group of people looking for a unique challenge.
Infrastructure isn’t required to be entirely functional. It can have aesthetic components as well. Also, a sliding bridge would require a lot of extra space on at least one side of the bridge that they may not have had space for.
I would think (but have no idea) that a bridge like this would have less routine maintenance requirements that one that slides or lifts as well.
In any case, here’s a stop motion video of it rolling.
