the reason they have not done it already is because they are still rolling out the traffic shaping equipment to all areas, to deal with the abusive users who think they are actually paying for that much bandwidth so use it like a dedicated connection
they are still rolling out and testing the traffic shaping equipment, which the handful of users on 10Mbit forced them to get by "testing the connection" 24 hours a day 7 days a week... i certainly hope that when they bring in the 20Mbit service they do go with their planned throttling policy and cap them to 1 or 2 Mbit during peak time so they can't fuck up the other users connections as much - although i suggest they have 2 policies for normal users being capped at say 2Mbit during peak time, and abusive users being capped to 256k during peak time, which is plenty fast enough for anything they can realistically want to do except heavy downloading, which any fair person would do during off peak time to avoid causing problems for other users