Honestly, it is quite useful for niche/startup sites. I have been on both ends of conversations that began from seeing these in web analytics (as someone that saw incoming traffic from a site and reached out, and as someone that received contact from a site I linked to) - and both times it ended in a mutually beneficial partnership.
I can understand the privacy argument to some degree, but it provides no more information than the standard Referer header (and if you use analytics like Simple Analytics/Plausible, it is a lot more visible).
Why? Already getting traffic for free.
Query string additions are commonly used to track things. You can see that lots of people don’t want that by the existence of Firefox features like “copy clean link” and Extended Tracking Protection which proactively strips some like UTM parameters.
Some sites happily participate in what I will glibly call the tracking economy. They may benefit because the recipient will see in their logs that lots of people are coming from their site, and do something that helps their site because of that.
My rejecting query strings is a simple form of protest against that system.
I say I’m broadly anti-tracking. I think it’s clear by this point to anyone with a skerrick of wisdom that the logical extreme of tracking is bad. But for a long way it seems innocuous. So how far do you go before declaring it unacceptable?
I hold myself to higher standards than I will hold others. For myself, I find it is most reliable not to start. I will occasionally show others this attitude or try mildly to recommend it, but largely that’s up to them.
I hate ads (in which I include billboards, newspaper ads, display ads, search ads, Facebook ads, sponsored posts, and a whole lot more; but not first-party stuff, and if it includes content not directly related to what you’re selling, it will probably be exempt too). I block ads as far as I can. Therefore I will never foist ads on others: t’were hypocrisy to do otherwise.
I like clean URLs and also hate precise tracking. Therefore if I send a newsletter-style email, it will include plain URLs that don’t track. So I can’t measure “campaign success”? C’est la vie. I’ll survive. I don’t want to scale anyway. I want people to respond by email, and respond to them. People are what matter in this life, even if I find computers far easier to deal with.
I dislike tracking where it is not functionally necessary. I confess that I haven’t yet taken this to the logical extreme of not recording server logs at all. I won’t ask clients what they are and where they’re from, but if they tell me, I will still record it for now, I guess. I might go more extreme on this in the future. But when some third party tries to force others to tell things unwittingly… that I don’t like.
Some web pages don't send referrers by making all links rel="noreferrer". Mastodon used to do this by default, though now they've changed their stance.
Links opened from non-browser apps don't have any referrer information either. E.g. if somebody shares your link on iMessage, WhatsApp, or Telegram.
Email clients may also strip out referrers, but I'm not entirely sure about this one.
If people read your work via RSS readers, you'll almost certainly not get any referrers. Unless it's a web-based reader like Feedly.
My website gets a lot of traffic marked as "Direct / None" by Plausible. I suspect this is traffic from RSS readers or Mastodon, but I can't be sure. A few times I've considered adding a "?ref=RSS" to all URLs served to RSS readers and "?ref=Mastodon" to everything I post on Mastodon. But like the author of this post, I feel uncomfortable tracking my readers like this.