But why do they need them? (warning, litteral answer ahead)

Because the makers of the app want to use location to obtain better quality adverts for the financial return of their app. (or at least, their agents/brokers who place the ads want to do that on their behalf).

If you are playing a game or an app with litte monetizable intention-orientated behavior (eg a shoe shopping app would have shoe orientated adverts) then you need to use something like location to at least get one dimension of context.

If you don't want the GPS locations going up, perhaps you should buy the paid version of the app (most do have a paid, no-ad version).