Cards are significantly different from a token in a phone:

1. They are physically separate. They are not likely to be stolen at the same time as a phone. 2. They do not require battery.

Cash has the same advantages, but even more so as it does not rely on networks at all.

If you only have phones as a means of payment what do you do if you phone is lost, stolen or out of battery? How do you even buy a new phone!?

I think phasing out cash is very short sighted. It is robust and reliable. There is a good reason the Swedish central bank recently recommended that people keep a certain amount of cash at home (1,000 SEK, equivalent to about £80/$108/94 EUR, per adult).