I don't think the main users of these services are Twitter users as you can't log in to Twitter using the alternative frontends, nor can you follow accounts to create a timeline afaik. They're just for viewing tweets eg if someone has sent you a Twitter link and you want to see what it is, or for conducting open-source research on what a person has said or put out historically. At least that's how I use them.

Governments and social services first.