why does the phone need a sim to operat? is account info on it? topic

howdy folks,
from what i have read these new generation of sprint phones with sim cards only store the login info for the LTE data connection, is that correct? the sprint cards are just basically RUIM cards right, but the slot can accept gsm cards for gsm network usage?

if i understand right they still have the voice and text account info on the phone correct? so why do they need the sim to operate? i'm just a little confused because my old world phones, TP2 and OZONE could operate without the sim in them?

thanks in advance


cheers,
disco