So, admittedly lazy, have not researched this.. But, as I understand, XRP will be a bridge currency, e.g. Business A in US wants to pay Business B in Mexico, so Business A sends payment to bank C in US, bank C in US buys XRP (via ODL) on an exchange for X Dollars. XRP is sent to Bank D in Mexico, Bank D in Mexico then sells X XRP on an exchange for Y Pesos.
All of this happens within 3 seconds. Why would any banks need to hold XRP for this transaction to occur? Is my understanding correct?