Other purposes? It's easy! You can make people avoid businesses that didn't paid to you and make them drive close to fastfood that wanted advertising. Or you can drive people around some political protests...
I recognize that they have been caught with their pants down with things like altering search results [1], but making broad speculative claims like this about the real world without any substantiation whatsoever is unfair and alarmist.
[1] https://www.wsj.com/articles/how-google-interferes-with-its-...
Alleging that they're actually doing that is one thing, but simply recognizing that they can do it and have a potential incentive is another and I think that is clear.
I suppose it is not _entirely_ out of the realm of possibility, but I'd be willing to bet that they won't end up taking that "route".