i don't know why this wasn't implemented a long time ago.
Japan has had NFC's on their phones for over 10 years... which was the last time i visited, i watched in awe as a girl purchased a drink from a vending machine by putting her phone up to a scanning plate.

Anyway... i want this on my phone, like NOW.
I use my card for everything and it would be much easier to just pull out my phone and wave. I'm sure they will also develop apps for budgeting and automatically categorizing my purchases so i can see all my income and expenses.
Also would help with any tax prep too. Kinda like what Mint.com does right now.