Yes, the $20 fluctuates in real global value but never while you're in a queue at a coffee shop. I still believe retailers only accept it to get on the news as a form of cheap publicity. The amount they take in revenue is a miniscule amount and they cash it out straight away - it's more of a "why not" option for them IMO. The advertising would cost more.
I actually believe there are lots of lies told about bitcoin - it's reliability and it's anonymity. Take for instance the identity of wallets - once you link an identity to a wallet then you can see ALL the transactions done with it. Really? People want that? The public have been asking to have their purchases made public to all and sundry? The anonimity that the drug dealers and gambling sites like only work when it's small and unregulated, not when KYC and AML compliance are factored in.
These are where I think the majority of people involved in BitCoin are simply dishonest about what it is and how it works and what problem it's suppsed to solve. Really, the only problem it does solve is "how can we also get to act as financial middlemen and take a slice of thew lucrative payment pie". It really offers very, very little to consumers which is why consumers are not using it and won't until it changes dramatically.
Once you strip away the hype and speculation it's really not that compelling as a payment system - most efforts underway are trying to turn it into a copy of existing systems or add it into existing processes (really, adding another layer will make things cheaper and more efficient?).
Ultimately, it comes down to trust. We're supposed to 'trust' some unknown people who may or may not hold the keys to all the currency vs the governments and financial systems. Yes, these have their faults but the current systems were put in place as they are because of how banking used to work in the past and the governments have a vested interest in keeping their currency systems operating.