I am visiting Berlin at the moment, and I miss the convenience and speed of being able to pay with contactless, by card or phone.
Regarding the speed of transactions: cash might be faster than signature or even Chip+PIN, but is surely not faster than contactless.
For example, anyone with a contactless Visa/Mastercard or phone can enter the London Underground by simply tapping at the barrier. They do not need to have a pre-existing relationship with Transport for London, to buy a ticket in advance, or to preload a stored-value card (as you generally must do in other city transport networks). And the ticket barriers open on average in 480ms. [1] That's pretty fast. You can't even pay by cash on a bus in London any more.
My example was to give quantitative evidence for the speed of contactless transactions.
It is true that there is no barrier in Berlin, but you still need to buy a ticket. For casual users such as myself, who don't have a season ticket, this takes significantly longer than 480ms: find ticket machine, queue, navigate menu, insert cash, wait for change and ticket to be printed, find ticket validation machine.
It is quite possible to miss the train here by having to queue to buy a ticket, particularly in busy places like the airport. This could be avoided if the tourists were able to use their existing cards/phones to tap in.
Regarding the speed of transactions: cash might be faster than signature or even Chip+PIN, but is surely not faster than contactless.
For example, anyone with a contactless Visa/Mastercard or phone can enter the London Underground by simply tapping at the barrier. They do not need to have a pre-existing relationship with Transport for London, to buy a ticket in advance, or to preload a stored-value card (as you generally must do in other city transport networks). And the ticket barriers open on average in 480ms. [1] That's pretty fast. You can't even pay by cash on a bus in London any more.
[1] https://www.whatdotheyknow.com/request/payment_methods_time_...