OK, but it isn't the simple fact you are reading text. If you are in an application, there is the processes associated with running the application and whether it requires an active data connection, location, etc. Oh, and all the while the screen is on and the phone is still keeping tabs on your signal strength, remaining battery life, etc. You can say you aren't doing a lot on your phone, but your phone is doing a lot in the background. Whether it should be taxing the hardware as much is another question.