I suppose you could say that it's not useless, but it's use is subsidiary to the primary purpose of thinking, because it is thinking that actually solves problems.

This isn't necessarily true however, on a group selective level, remembering allows you to more effectively pass information to future generations, allowing your community to continue to adapt socially to your environment.

Sheep do this, with young sheep being explicitly taught how to handle a landscape by their parents, which is normally understood as showing them how to walk etc. but extends all the way to navigation and safe routes at least.

In our context that connection is far more obvious, even if that purpose has been in many ways assumed by tools; even if your brain remembers things solely for the purpose of thinking, it may not be for your thinking, and so we can say that memory, on an individual level, has a separate function.