I've never heard it called "people's key" but a lot of rock and popular music written in the past 50 years was written on guitar where these keys are the easies

I've never heard it called "people's key" but a lot of rock and popular music written in the past 50 years was written on guitar where these keys are the easiest to play. I imagine Am/C are easiest on a piano but I am not a very good piano player to begin with.