This has been a slow process for about two years now I think, and has recently gotten a lot worse.
In the past, Twitter would sometimes show errors instead of tweets when not logged in. My assumption at the time was that they were prioritizing logged in users during high traffic hours, but who knows. Then they required you to log in when trying to view the media tab on profiles, and from there it sort of snowballed into its current state, where you can scroll down a couple tweets and then get the full Pinterest experience.
In the past, Twitter would sometimes show errors instead of tweets when not logged in. My assumption at the time was that they were prioritizing logged in users during high traffic hours, but who knows. Then they required you to log in when trying to view the media tab on profiles, and from there it sort of snowballed into its current state, where you can scroll down a couple tweets and then get the full Pinterest experience.