Client have to be easily accessible, meaning that general people could adopt and use it. Notebooks and desktop computers aint nowadays even used in every household, i know many folks who just mainly use their tablets and smartphones. I dont know about rest of the world, but in Finland banks have very sophisticated clients/internetbanks and with all the NFC and other mobile payments systems, competition is fierce.
Certainly NEM have to be better than those systems of we want to create complete currency system/finance platform.
We definitely shouldn't forget about smartphone users here. It's a vast and growing market.