Re: What study?
Aldi now take contactless credit and debit cards.
I've found using contactless cards (with the exception of an American Express card which doesn't seem to work everywhere) really easy and thankfully more places are taking them now. The only annoyance is the few badly-trained cashiers in some shops who insist on having you "insert your card" before they will activate the card terminal meaning by then it's too late to bonk.
Considering how easy a contactless credit card payment is, I can't see why I'd want to use a phone to do the same thing. The card payments are quick, easy and just work. No batteries required.