If your starting premise is incorrect, the rest of your assumptions will be wrong too.
Yes, people use Bitcoins to transfer VALUE, that's what all money is for.
But the value doesn't have to be expressed in fiat currency. The more bitcoin
is widely accepted, the less need there will be to convert back to fiat.
People also use it as a store of a value, a hedge against inflation, and as you point out,
it is superior for transfer. This has uses for remittances and ecommerce, and the
superiority lies in its divisibility, speed, and low cost. Many would
like to see it become the dominant form of money, or at least money that they would
personally use.
Some people like it because it can't be confiscated, nor does it rely on third parties.
It can be easily hidden and moved across borders. There's so many advantages
over fiat money.
1)Ross Ulbright and SR shows they can be confiscated. Mtgox was "hacked"
2)If my local gas station accepts bitcoin, what must the gas station sell them for dollars, how does the oil get from the ground to my vehicle to move my factory farmed food from farm to table when 15% of the population is on food stamps...
Sorry for the run-on sentence but your view tooooo simplistic in an extra-ordinary very complicated world... And I am only speaking largely of this country only.
Ross Ulbricht got coins confiscated either through extortion or they had access to his computer.
Obviously different than freezing a bank account.