You mistake the medium for the end; in that – People want functional value; ie; people want valuable currency that can be traded with the greatest ease for the greatest profit; the medium of their currency (Euro, Dollar, Pound etc.) is only sensible in actualising a potential value, and is only contextually appropriate - ie; in general terms people will want a local currency because it makes it easier to actualise the value of the currency; however to
presume that this currency by nessecity must be the local one misses two key points:
Primarily, that the relative values of currencies fluctuate, and therefore it may not be sensible to hold onto a local currency if a nonlocal one is increasing in value (or yours decreasing), in which case one sacrafices liquidity for value.
Secondarily, when countries have financial crises, especially when entering hyperinflation etc. the reliance upon foreign currencies (for stability) can emerge, hence the reliance purely upon a national currency may not only decimate the value, but also reduce the liquidity of cash.
Ie; I am British, and in general terms I want pounds, for I can actualise these with regards for trade for local products etc. However, to me, value superceeds the currency, and if Britain was entering a crises and the currency was going lose value, it would be sensible to preserve the value in my money by placing into more stable currencies; even if this in the short term reduces the ease of trade.
Furthermore, the speculation that the dollars will eventually reach America is an unfounded one, as their use as currency can be maintained outside of America easily, so long as the realisation of the value of a dollar is possible outside of America (like in many poorer countries, especially ones with unstable local currency) – What would be a sensible statement is that
a currency (product) will gravitate towards markets where it’s value is realisable.