Because each UTXO is not the same. Specific UTXOs can be sanctioned.

They might transfer over the network, but good luck trying to buy things with UTXOs that the US has deemed to be bad. No legitimate business wants the hassle of getting their door kicked in by the feds. They just won't accept it. 

 Well that's a problem of treatability and yes, I see your point


Don't know what's gonna happens, we we'll see🤷