I don't really understand why social sites don't support a decent "read-only" mode. I get that someone having an account probably makes them slightly more like

I don't really understand why social sites don't support a decent "read-only" mode. I get that someone having an account probably makes them slightly more likely to engage and perhaps a little easier to target with ads, but it's not like read-only sites and services can't make decent ad money. And isn't it true that only a tiny percentage of social media users contribute? Adding needless restrictions to users who just want to consume content on your service seems like a really stupid idea when those users are probably the bulk of the user base and will bring in the bulk of ad dollars. Personally I won't use services that require me to sign up. I used to use Twitter quite a bit without an account to search for conversations about current topics or just look at the tweets of someone I'm interested in. Recently I've been forced to sign in to use search so I've just stopped using it. Maybe some people would sign up, but I'm guessing a very significant percentage people won't bother creating an account just to search for something on Twitter.