You're not sending money. You're sending tokens. People who say that they are sending money "on the blockchain" are being disingenuous.
You have to account for transaction fees into cryptocurrency, the blockchain transaction fee itself, and the conversion into the target local currency.
You left 2/3rds of that process out, conveniently.
Then you transfer to Exchange A and sell, and what do you get when you sell? Tether.
The point of Tether initially is regulatory arbitrage for Tether based exchanges. It gives them a fiat substitute without having regulatory baggage that trading in actual money would require.
Tether then turned into a lifeline for a Bitfinex bailout and now acts as a (almost assuredly illicit) liquidity provider to Tether based markets.
The only reason Tether is worth a dollar at this point is because the Tether denominated Exchanges say it is worth a dollar. They are really what backstop Tether now and are fully complicit.
Bitcoin doesn't solve any trust problem outside of how many bitcoins are in each wallet.
Even in the very basic ecommerce use case: buyer purchases item online with bitcoin. The buyer must necessarily trust the vendor to deliver.
There's no recourse outside of the good graces of the vendor. There's no chargebacks or third party mediation.
Thus Bitcoin actually reverses the risk assumed by online purchases from the vendor to the buyer.
This is the reason why Bitcoin is a failure outside of niche grey and black market concerns. It is far worse for the consumer than existing solutions that isolate them from transaction risk, and will usually kick back a small percentage in cash back.
> Broadly speaking blockchain only solves a singular problem: Trust
This is only true in the cryptographic sense when talking about data on the blockchain.
Blockchains do NOT solve any trust problem outside of data on the blockchain, and in real world use cases when we're not dealing with how many coins each person has in a wallet, this is the most important thing.
Specifically your cryptographic tamperproof data on the blockchain is useless if you have bad actors entering garbage data.
It's useless if the data on the blockchain is out of sync with state in the real world.
Even in the internet commerce use case where bitcoin was supposed to take over, once the bitcoins are transferred you still have the unsolved trust issue of verifying delivery.
Saying blockchains solve the trust issue in the real world is disingenuous magical thinking, and I wish people would stop doing it.