If you don't think anyone is going to call or message you put it on airplane mode to save battery. People think you just got back from holiday or an important meeting/business trip too.
Who listens to music from a phone's speaker? Kids and grannies with no tech savvy, not even smart enough to carry a decent bluetooth speaker or two. Humanity is doomed.
I listen to music from a phone's speaker, but because I'm tech savvy, I put the phone in an empty glass, the sound is amazing