Lets say that I want to open up a bank account and deposit 100$ in it. I go to the bank, they make me sign a few papers, I hand over the 100$, they give me an ATM card, and I'm all set to do transactions.
I assume you mean debit card because the ATM is only going to be able to give you your $100 back (in the best case). You also will need to present various papers when you go to the bank.
With Bitcoins, I have to install the bitcoin wallet myself, then transfer some money using obscure methods to MtGox or some other exchange, then buy BTC using an interface similar to buying stocks, then wait a bit for the BTC to show up on my wallet, then finally I am ready to do a transaction. Currently most stores don't accept it, so if I want to use my BTC in the real-world, I have to jump through the same hoops. And while BTC transactions themselves don't have, a lot of the ways to cash out do have fees, whereas many of those that don't have "real" fees will not give you fair rates for your BTC.
So for the typical user who doesn't buy online normally, it's not a very convenient currency yet.
True, not so convenient yet especially for the places that don't accept it. But suppose you want to send money overseas to your friends or accept money online as a business? There are still hoops to jump through but it shows the promise of being more convenient than anything else out there.