Banking eradicates many of the supposed gains of decentralized money - not all, but most. I just dig a quick Google for "benefits of Bitcoin" and it seems most people agree on the following:
- Anonymity/trackability. Gone if you are with a bank. Sure, possible to sidestep by going through the song-and-dance that is withdraw-send-deposit. We can do this IRL also, but there's a reason people do not.
- Taxability. Welp, if your BTCs are in a bank, the IRS can easily get you.
- Abusive/coercisve government action (e.g., freezing). Well, yeah, if you're with a bank that can happen too.
- Lack of fees. If banks become standard (and if BTC takes off, yes, they will become standard) then kiss goodbye to this benefit - the same way cash right now has no transaction fee, but bank transactions do.
In fact, the only major sell of Bitcoin that remains:
- Inability for government to arbitrarily expand the supply of money.
Still a win, but suddenly Bitcoins have lost a lot of charm, especially for the everyman for whom the above 4 points are much more salient than that last one.
- Centralized money is bad! We need to create a perfectly decentralized, distributed economy!
- Oh no! It turns out that the average Joe will get burned really badly by this new decentralized system!
- But wait! What if we created these things called "banks" and provide people peace of mind and security by taking on some of this risk?!
- ...?
- Um... not profit.