You certainly don't need gloves for road cycling but plenty of riders choose to use them to protect their hands and if you are relatively new to cycling you may too.
You will see the majority of pro riders in gloves because they spend hours every day riding a bike which will take its toll on the hands over time. Gloves also protect the palms of your hands in the event of a crash.
For amateur cyclists who don't spend nearly as much time on the bike the need for mitts is a little less pressing but for long days in the saddle or summer rides when your hands might be sweatier they can really help improve comfort, try them and see what works for you. Some riders choose to wear no gloves a lot of the time because they prefer it, this is fine too.
In some cases, if riders are racing on the track in particular or in some road or circuit races, particularly for young riders the race commissaries or officials will stipulate gloves need to be worn to compete in the name of rider safety. So it's often worth keeping a pair of gloves in your kit bag just in case.