The reason that everybody is trying to move to this type of things is the success of the London oyster card system. Not perfect, but good enough, and is widely adopted.
The key with the London system was the transit fare system was very well integrated to start with. If you bought a zone 1-4 weekly pass, you could take buses tube and trains everywhere within zone 1-4.
The trick to getting adoption was the cash "penalty" fare. For instance a cash bus fare is nearly twice the price of an oyster card fare. And if you buy a season ticket it gets loaded onto an oyster card. So anybody in London needs an oyster card, and so has one.
The other effective thing that was done was to only have oyster top up and ticket sales at stations and offered exclusively to local independent corner stores. The advantage to the store holder is 2 fold, it gave a small financial return to the store owner, but more importantly for the store owner it got people in the store. Topping up oyster cards and at the same time getting a drink or chocolate bar etc. So very quickly every store had one, and in London there are a lot of them so it was widely accessible with very little staffing costs.