The money from cash cards can also be used to buy loads of fuel from a certain gas station, which is very useful. There are also vending machines scattered about, but you could just smash those at the cost of spawning a law enforcement eye bot (easy to avoid).
As for the npc’s, they are still very much in their early stages and are planned to get a lot more attention somewhere in the future.
Feel free to ask any other questions, I love to share what I have learned from this game!