Been sailing since 2012 and can't remember when someone on their phone has bothered me.
Sure it can happen, but I can tell you this, there is no way that a major cruise line is going to start blocking cell phone usage... either calls, texting, surfing, etc... if anything they are racing to see who can provide the most access.
The problem isn't cell phone access, it's rude and oblivious people. Rude and oblivious people exist everywhere.