For some links it makes little sense to define UTM parameters. Especially for internal links, you should refrain from doing so. If no UTM parameter is defined for a link, Google uses three different factors to evaluate how the visitor came to the website. 1. organic: This criterion shows when the user visits the website via the search engine results list. 2. refferal: This shows if the visitor came to you via an external link from another website. 3. direct: This section displays traffic that comes via direct entry in the browser, the bookmark function or, for example, via links (without UTM parameters) from newsletters. With these three output values you can already read a lot about the usage behavior of your website. However, the targeted evaluation of campaigns will be difficult for you. Since the data cannot be selected more specifically, it will be more difficult for you to see whether your advertising measures are running as planned or need to be optimized. For these purposes, the use of UTM parameters makes sense for you.