Transportation options vary from island to island. Many visitors enjoy taking bus tours to conveniently explore the Islands. For most islands you can also get around by shuttle, taxi, ride-sharing app such as Uber or Lyft, or public transportation.
Is it worth hiring a car in Honolulu?
If you do want to sightsee, it will be much easier with a car. One major benefit is you'll be able to do things at your own pace. Oahu isn't big; without stops, you can drive around the island in about two hours. That said, there are things you might want to see and do that aren't accessible by public transportation.