1) Patterson child really needs to go somewhere.
2) Patterson child is forced to rely on the (illusory) good will of his/her mother/father to get there.
3) John and/or Elly act like surly jerks because they think having to unclench their sphincters and go somewhere they don't usually go at a time they're usually at home is some horrible sacrifice.
4) John and/or Elly bristle at the idea of letting the kids have access to transport of their own because of an exaggerated and/or mistaken belief that their children are trying to bankrupt them.
What John and Elly don't see (because they have not much in the tank brain-wise) is that their default refusal to see that their surly need to dictate how the kids get where they need to get is going to backfire on them. Mike's wanting to believe that the bus company is also going to charge the earth to get where he needs to go because adults like his dad want it that way is a symptom of John's short-sightedness. Elly's imbecile refusal to pay to fix Liz's car directly to her getting a motorbike so it too is a symptom of a Patterparent being a dimwit. Ah, well. At least they get their own back when she wants to impress strangers and jam it to Mira being generous. They put their cars in the garage and leave Mrs "Only MY Time Is Important" out in the driveway chipping away ice as she bellows like the idiot she is and brandishes an ice scraper like a sceptre of failure and shit-for-brains stupidity.