I am a long time member over at XDA and am very familiar with rooting, modding, third party ROM's, hidden and factory menus, and so on. I have been using Android devices since the days of my T-Mobile Sidekick 4G, which came with Eclair and got a Froyo OTA about 8 months after the device launched. This is partially why I am very picky with the devices I choose to use daily. I was a big fan of Nexus devices but I am not a fan of ht ePixel devices. The function is still there but the looks of the device definitely are not. 😛
Carriers locking out things from users is nothing new, especially in the US, where I spend a lot of time. My girlfriend and her parents are on AT&T, which has to be one of, if not, the worst US carrier for deceptive and greedy practices. It definitely sucks that carriers, especially Canadian carriers choose to implement these dishonest practices. Sadly, regulatory bodies like the CRTC allow this to happen with some clever exchanges of money, which is also why we don't actually have true competition in our cellular, internet, and cable companies.
Depending on the device, sometimes root can bypass the lockout of certain settings by using things like Root Explorer with root permissions to activate the apk where these settings are contained. Third party ROM's can also remove these restrictions from devices where they are enabled. Some devices do have engineering or factory menus that can also help with those settings. Even though those dialer codes can usually be found on the internet, you can majorly mess up your device if you don't know what you are doing. The amount of posts I have seen on various different phones where people have completely messed up their phone, rendering it saying, "No Service", even after a factory reset for messing with the LTE menus. If it is really important for anyone to have specific settings available to them, then check these things when you first buy the phone without your SIM in it and then after you put your SIM in it. Most carriers at least have the 7 day buyers remorse return policy as long as you haven't used 30 minutes of airtime and more than a few megabytes of data.