It seems like this exploit is targeting those that keep their phones tethered for connectivity outwards or hooked a USB modem or a SIM card into a cell-equipped headunit.
The only valuable thing there is the relatively 'clean' mobile connection... and this malware's dropping a residential proxy endpoint on the headunit to take advantage of it. Bonus points if the headunit is always connected and always powered up to a +12v rail in the car, that's free and always-on real estate!
Head units aren’t always-on. Typically they go into a low power standby 2-5 minutes after ignition / accessory mode turns off, and go completely power-off 30-ish minutes later.
Otherwise any car sitting unused for a week or two would have a dead battery.