Marketers use UTM parameters to help them see how engaging different traffic sources are. They let them unpack a traffic source from just say ‘Facebook’ to ‘Facebook Campaign 1’ and ‘Ad Creative 1, 2 & 3’. They can use this fidelity to see how each has performed and make adjustments accordingly.
It’s also a bit of an insurance policy, you may not know what you need to improve over time. But if you have set up UTM parameters at the start of a campaign, you are better placed to find areas that aren’t improving and stop them. And move resource to those that are working. It’s kind of making a future you, better placed for success.