alt Hacker NewsI'm not sure what Twitter's specific reasons are, but AFAIK the general trend of login-walling services over the past few years has happened due to a court decision saying that it's legal to scrape publicly available data ( https://en.wikipedia.org/wiki/HiQ_Labs_v._LinkedIn ). If they gate content behind a login wall and put a clause in the EULA forbidding scraping, this lets them use the CFAA to go after anybody who still scrapes the site.
Effectively it forces scrapers to become a party to the terms of service, which usually contains the "no programmatic access (other than via paid API)" or specifically prohibits automated scraping.