Most people root to "gain control" of their phones. My last 3 phones were rooted to remove carrier bloatware, use AdAway, and backup apps and data. The backups came in handy, because if a developer or Google updated an app and the newer version was "crappy/buggy", I could revert to older version.
So..... If phone is truly running a Google/Android OS, not some carrier branded version/manufacturer version (Blur/HTC), phone won't have bloatware. Launchers can change look of phone. Issue one is mainly solved. AdAway (or other ad blockers) can sometimes be used without root. Problem 2 partially solved. As for #3? Kind of a biggie for me. Some apps have newer versions bi-weekly. Most are garbage. No way to revert back!
When the "powers that be" decide features that I actually chose my phone for are "no longer needed", I have an issue. Anyone remember the Original Droid? When the system upgraded from "Froyo" to "Gingerbread", Motorola decided the blinking led was no longer needed. First time I rooted. I WANTED and NEEDED that feature for various reasons. I chose that phone for that feature. I needed a ROM to put back a feature someone else took away. On MY phone.... What would prevent them from disabling something else? "You don't need a speaker phone.... You can pay for visual voice mail..." Can anyone else see a carrier forcing you to use their navigation system on their branded phone and having "your device is incompatible with this app" appear on the Playstore? Yeah... Too scary to even think about....
OK... Rant over....