I think the title bar on the top of some web browsers is not as useful thesedays since most web browser tabs also show the title of a website when you hover your mouse's cursor over a tab.
Not necessarily true, I still find the title bar convenient to have.
It creates a bit more space for tabs, and it's easier to drag the browser window around if you don't maximise it.
Luckily, Chromium offers an option where you can choose between using a titlebar or not (at least, in the Linux version).