Navigation is thought to be central to the evolution of our cognition as it is both complex and essential for survival and propagation, hence the "the method of loci" as a memory tactic. Walking was the primary or possibly only time when navigation was important for most early people..

Does there have to be? Doesn't evolution produce a lot of things which are side-effects not goals?

yep. the biological term is "spandrel"

https://en.wikipedia.org/wiki/Spandrel_(biology)

Evolution doesn't care as long as you reach reproductive age and carry out that task properly.

... and live long after that in good health, to support your offsprings and help them succeed in their reproduction.