The fact that Bitcoin functions Outside of the Banking, Governments, and Tax control systems is a big Plus.

But it is also a huge minus:
Indeed, in order to Buy Bitcoins (BC), people need to convert their Fiat money (USD/EUR/CAD/CHF, etc) to BC by using the services of Exchangers.
The same thing is true for Selling / converting whatever BC they own back to Fiat. The same principle applies to Debit cards.

Exchangers take their In-exchanging customer's money (Bank wires, Credit Cards, etc), and Fund their customer's BC account with BC they had previously bought, or using BCs from Out-exchanging customers to whom they'll pay Fiat (or credit their Debit card, etc).

This means that regardless of the transaction type (Buying, or Selling), BANKING transactions (using traditional Banks) are involved.

And this is where the minus comes:
Whenever the Banking system (Cartel) will feel, or decide that Bitcoin is a threat to their revenues, or model, or their respective governments will decide to put pressure on them to do so, because of "Lack of Control", "Terrorism Funding", "Tax evasion", "Kiddie Porn", "Drug payments", and other illegal things, Governments, and Banks will use the power that they have to stop the Exchangers' businesses, simply by closing their bank accounts, one after the other...

The end of Banking for the Exchangers will simply mean the end of being able to Buy, or Sell Bitcoin.

And untill someone finds a practical way for people to convert Fiat to Bitcoin and vice-versa without using the banking system, this would (in fact WILL, because it's only a matter of time for it to happen) unfortunately be the end of that :-(