One way, two way, blue way! The foolish decision

I want to tell the story of two outings with a friend's family.

Outing #1
It is someone's birthday.
Because we have no car, her mom drives out from Denver to pick us up in Boulder
Then she drives us back to Denver for the party at her place. When we arrive in Denver, she decides it's important we go swimming after the party,
So she drives us back to Boulder to get our bathing suits
And then back to Denver for the party.
Then after the dinner, we drive to Boulder to go swimming
And then drive back to Denver for the cake
And then she drives us back to Boulder when it's time to go home
And then drives herself back to Denver for the night.
I estimated that we drove over 200 miles.

Outing #2
It is someone's birthday.
Because we have no car, we are picked up and driven into Boulder to go to IHOP.
When we're done eating, her grandma has a migraine.
The first plan is that an aunt will take Grandma home first, then come back for everyone else.
The second plan is that we will all get in the two cars present and go home together, since we can all fit in the two cars.
A short while later it turns out that the first plan was enacted despite the second plan. We all sit out in the hot sun.
Then the decision is made that all the people staying in Boulder will get in one car, and all the people who need to be dropped off at Longmont will get in the other car
And then both cars proceed to go to Longmont
Drop us off
And drive back into Boulder, where they totally were in the first place.

Question
Why do these people waste so much gas?