This slight delay and small breaks in the day have been implemented to help prevent the widening of spreads during this time when liquidity providers go offline. The liquidity of particular currency pairs is also dependant on the time of the day. This is due to the fact that trading volume plays a pivotal role in the liquidity of currency markets.
For instance, the EUR/USD pair will experience high trading volume and liquidity during the confluence of the London and New York sessions, that is, when the two sessions overlap. This is the point in time when the highest number of traders in the United States and Europe are online.