I imagine that they have two motivations in mind:

1. Get more useful data from users like myself who have a Twitter account but are not logged in by default. Every time I click on a tweet that a friend sent me by IM or that I saw linked elsewhere, they are not getting that juicy detailed data regarding my user having seen this tweet.

2. Just assume that mainstream users will simply go "Oh well, I'll make an account" and think nothing of it.

They still have cookies and your browser fingerprint. You might be surprised how complete their picture already is.

They would if I meant "not logged in by default" on the same browser, but I mean on completely separate devices which have never even touched my Twitter account—not out of paranoid sandboxing on my part, mind you, just no motivation to log in. I barely tweet anything at all, so why bother login in.

Could they still know it's my "user" who is seeing this or that tweet, by using intelligence-agency level analysis on usage, personal connections, and networking patterns to determine that it's me? I'm sure they could. But why bother to such a massive level of complexity when they could simply require login to view tweets instead?

Have you been introduced you to Firefox containers? Best feature the masses will never use.

I am thinking that Twitter has reached saturation for the most part. Pretty much everyone has heard of it and has an opinion about it. The areas of the world that do have an untapped audience also have authoritarian regimes that do not like Twitter very much.

At the same time, there is some manager with a spreadsheet that has new account creation metrics. S/he wants that number to be as high as possible. How do you do that if people do not actually want to make an account? Try capturing the people who usually click in from other sites and bounce back.

I think the end result will be that social media somehow becomes even more pictures of text than previously.

It's being spreadsheeted to death. When, as a manager, all you look at is some Excel spreadsheet that tracks the numbers you think are important, you get reactionary management.

Chasing metrics.

KPIs can work well or not. In this case, some VP's KPI about increasing signups and % of tweets viewed by signed in users is making Twitter worse (actually better because I hate Twitter).

To draw back in those seeking to cut down their social media usage, in part

I don't see how that makes sense. If you're looking to reduce your social media usage, this change will make that easier..

One way of cutting down usage is to reduce the amount of data you volunteer. Logging out is an easy way to reduce usage. This change compels light users to stay logged in and participating.

Thanks for the considered responses, this was all super illuminating! And thanks for the hot tip on Firefox containers too :~I