Many people are visiting your web site. If you’re a commerce web site, they may be interested in your products. If you’re a blog, maybe their completely enraptured by every word you have to say about a particular topic, whether it be your latest travels or latest conspiracy theory about fluoride in the water. Or it might be people just passing through, who read your content, shrug their shoulders, and move on.
Most sites, can’t be everything to everyone (some e-commerce sites being a possible exception). You can’t appeal to the flat-earthers and the sane people at the same time.
From a web analytics perspective, it’s important to know the web behaviors of those you want to engage with the you site. If you are some sort of a whack-a-doodle peddling some sort of edge-case theory about the aliens living among us, you want to optimize your site for those people. It’s likely though that you may have other people visiting your site.
At any rate you have a certain audience in mind, the people that your web site exists for. You want to know what they are doing on your web site, and whether you are engaging them in the way you want, whether it’s spending time on your site, reading your content, donations, buying products/services, writing to their congress person, etc., etc.
You’ll want to isolate the web behavior of your target audience, so you know how to reach out to them, what content to path them through on your web site to meet their need.
And don't fall into the trap of awareness. “We should pursue this direction with content or site features, not because it’s directly impacting our target audience, but it's building awareness for customers/donors/engaged users of the indeterminate future. You can justify doing almost anything for awareness. But how do you measure whether you are being successful making the leap from awareness to active, relevant user? Some survey work, possibly, but unless you have unlimited resources, where do you want to expend your effort? The prospects you can directly impact now or the maybe prospects of the future?