Why does Casey Anthony deserve a death penalty? Why not life sentence?

Why Casey Anthony deserves death penalty for the murder of her daughter? Why not life sentence because death penalty sounds very serious for a case like this. It's just that Caylee wasn't tortured or abused when she died except being suffocated with duct tape because either Casey was tired of watching her kid and wants her freedom back or she and her dad is nuts enough to kill her (her dad wrote suicide letter to his wife Cynthia he sounds guilty because he mentioned being innocent in letter and planned a false suicide death to deter police from him so he won't get in trouble) whatever what the heck went on, why does she deserve such serious and maximum penalty?