It's not necessarily about tinkering and you certainly don't have to flash a custom ROM. Many root just to obtain full administrator access to the device to be able to make a few simple changes you otherwise wouldn't be able to do. One that has been mentioned a few times here is ad blocking via a custom hosts file. In order to do that you need the proper permissions (write/modify) to that system file, which root access provides. Another one I mentioned previously is re-enabling infinite scrolling of home screens and app drawer, which is also just simply modifying a system file. Again same thing if you wish to kill the OTA updater (although there's a non-root method now for the Note 4. See my previous post). So root access just gives you more options if you want/need them.