Because the addition of hundreds of vendors over several months does not constitute "take-up" by the market.
Take a look in detail at the sites accepting Bitcoins. The vast majority of the software services provided are not for sales, but accepting BTC donations. I decided to make a random sample of sites advertised under Educational Software.
- OpenEmulator (accepts donations in BTC).
- ActiveGrade (no longer accepts Bitcoins).
- Popup Chinese and Popup Cantonese (same business, free registration, not clear it accepts BTCs).
- Project Fedena (no indication that it accepts BTCs).
- Question Writer (accepts BTCs).
- AssignmentHOLE Tutorials (accepts BTCs).
- SimplyMaya (accepts PayPal, no indication that it accepts BTCs).
- Flash Card Maker (accepts credit cards and PayPal, no indication that it accepts BTCs).
The same can be seen in almost every sub-heading. This is not the sign of a growing and vibrant economy.
Because exchanges which are trading 20,000 bitcoins a day have no liquidity.
Liquidity in Bitcoins, as in currency circulation you know, people using the currency to pay for things. There is mostly hoarding and speculation, this is the opposite of liquidity.
Because dozens of secure exchanges to chose from means all of them must be "dodgy".
Secure exchanges? One word. MtGox. The exchanges are laughable small-time operations that rely on the financial cluelessness of the libertarians and teenage hackers that make up almost the entirety of the Bitcoin economy. I notice that you failed to answer the comment about Dwolla. This is a huge blow for BTC (yet another one). The only reason why it is still alive is because of True Believers like yourself.
Because scams and hacking never happen with normal US bank accounts.
The law protects me against such scams. For example, in Europe I am protected in case of fraud almost for the entirety of the transaction. If someone hacks my bank account I have access to the legal system.
If someone steals my BTC wallet, tough luck.
Yes, I can see why Bitcoin is taking off so well (hint: sarcasm).