I find it fascinating that in the US, manufacturers are offering cars in the 'luxury' sector without navigation. Here in the UK, that wouldn't sell a single car in the luxury sector.
I've had about fifteen rentals in the UK in the last year, mostly compact size. More than half of the cars I've been allocated have factory fit navigation. I'm in a Ford Focus this weekend - it's nowhere near the top spec for the model - but it has navigation built in.
Most rental fleets here are on manufacturer buy back, to feed nearly new vehicles into the dealer network forecourt, so the spec is chosen by the manufacturer. The manufacturers know that to move the vehicles through the dealer forecourt quickly, they have to offer navigation.