Because the user experience sucks. I hate copying a URL and have a bunch of meaningless garbage included in wherever I paste it, as happens with pages that leaves UTM artifacts in the query string.
I don't care at all about the tracking aspect of removing UTM, I care about how it makes the internet shittier to use.
Exactly. But not just when copying a URL. Short, simple URLs look nicer and feel better. This is basic web design, but somewhere along the line we've allowed salesy/marketing nonsense to infest our web.
This spells out the issues really well (with a funny video) https://wistia.com/blog/fresh-url The suggested solution on there "Fresh URL" is interesting, although it's throwing more javascript at the problem.
I don't care at all about the tracking aspect of removing UTM, I care about how it makes the internet shittier to use.