Q: Battery Percentage does not feature when IPhone is switched off and On charge

HI Everyone  

I am new to Apple as a customer so still getting used to the phone and it's features.

I recently bought the Iphone 6S plus  and noticed that when I charge it and it's powered down or turned off it does not show the battery as charging or how much of the battery has charged like in an Android phone where when you turn off your phone and charge the Battery sign comes up displaying the percentage as the battery gets charged.

P.S I am aware of the Battery percentage viewing aspect available but that only works when the phone is powered up as in when the phone is turned  on.

Would appreciate an insight as to whether IPhones as a thumbrule Do not display Battery charge percentage when turned off and charged or Should I be concerned ?

Thanks in advance

Kat (>"o"<)