The primary motivation for rooting the phone in order to be able to modify the hosts file was to block ads in ad-supported free apps. Another low-tech method for achieving this was to put the phone into airplane mode while using the apps.

When it comes to the browser itself, another common method for adblocking was for the adblocker to function as a proxy server that you'd setup in chrome, and you didn't need root for this.

Also, you can just use Firefox for android, which lets you install same extensions as on the PC version, including adblockers.