Cars are definitely something that could be added to the game.
A lot of people just think of cars in there basic functions (getting from point A to point B) or for cosmetic reasons, but there are so many things you could do with a vehicle besides just driving.
The Sims 2 cars comes to mind as for what can be done with cars in the Sims 4, but I have some other ideas too.
First off car animations for getting in and out of cars/vehicles. Carpools! Two,four, and six-seater vehicles! Motorcycles, mopeds, bikes (child-elder), trikes for toddlers. There could be a five level bike riding skill for child sims with bikes having training wheels for the first two levels. Parents could help train them. Riding bikes could increase motor skill for child sims and fitness skill for teen-elder. Bikes could also be used as transportation (loading screen), or just ride around the neighborhood/ lot/ open space.
Mechanic career
A new career where your sim fixes cars for other sims.
Drive-In Theater
Watch a movie with friends/family/ or a date at the drive in theater.
Get To Work Retail
Make a car dealership.
Things that can be done in/to a car/vehicle with one sim:
- Sit in car
- Nap in car
- Listen to music/radio station, set volume (increases fun for music loving sims)
- Work on car (increases handiness or a new mechanic skill)
- Steal car (Kleptomaniac sims) (decreases responsibility for teens if you own Parenthood GP)
- Paint car (increases painting skill)
- Tag car (decreases responsibility for teens if you own Parenthood GP, increases mischief skill)
- Set ownership (teen-elder)
- Turn on/off lights
- Blow horn (change horn sound with high handiess skill)
- Change tires (increases handiness or a new mechanic skill)
- Check engine
- Wash car (increases responsibility for teens if you own Parenthood GP)
- Lock car
- Go for a joyride (rabbit hole interaction)
- Travel to... (loading screen)
- Install alarm (high handiness skill required)
- Disable alarm (high handiness skill required)
- Show off new ride
Things that can be done in/to a car/vehicle with two sims:
- Make out
- Woohoo
- Cuddle in car
- Kiss
- Listen to music
- Work on car
- Sit in car
- Go for a joyride (rabbit hole interaction)
- Travel to... (loading screen)
- Teach to drive/driving skill for teens only (rabbit hole with chance card prompts)
- Wash car
- Paint car
- Tag car
Things that can be done in/to a car/vehicle with a group of sims:
- Listen to music
- Work on car
- Sit in car
- Turn on/off lights
- Blow horn
- Go for a joyride (rabbit hole interaction)
- Travel to... (loading screen)
- Wash car
- Paint car
- Tag car
Sims can:
- Brag about new car
- Gift a car to another sim
- Complain about car noise (if car needs tuning up, car horn is blown)
- Complain about car
- Ask for a car/new car (teens only)
- Ask to teach to drive (teens only)
- Discuss car models
- Complement car
- Talk about cars
- Shop for cars online
- Sell car online
- Research car tips
- Give key to car
- Complain about stolen car
- Brag about new bike
- Talk about bikes
- Ask for a new bike
- Discuss fear of falling off bike
- Ask to help with bike riding (child sims only)