Especially for USD/HKD, as the HKD is pegged at HK$7.85 / US$1. The exchange rate rarely, if ever, moves away from that point, because the Hong Kong Monetary Authority is required to maintain reserves in USD to redeem HKD at that rate. Any movement in the exchange rate is essentially a bet against the stability of the HK government in general and the HKMA in particular -- you'd only see it if people thought that the HK government was going to collapse or be ousted by the PRC or something.