I would love for it to become digital cash, but the transaction fees are much higher than cash at the moment.
If you're talking about credit card fees, which are generally a fixed rate + a % (Stripes fees are 2.9% + 30c) then it's a hell of a lot cheaper for everything but the smallest of transactions.
You can currently get a transaction confirmed in the next block for around US $0.60 based on an average transaction size of 250 bytes and 30 satoshi / byte. With that $0.60 fee you can transfer everything from tens to millions of dollars. If the transaction isn't as important or you can wait more than ~10 minutes you can get it even cheaper.