Somewhat unfair to compare the Lakeshore lines, I agree, but don't forget that most trips are within the peak periods. At least
2014 is a good proxy of regional rail demand on the other 5 lines since they are only operating during peak periods; doesn't include the Kitchener's all-day service.
The biggest drawback is that Richmond Hill
IS in the Don Valley. That puts it away from any population until Don Mills north of Lawrence, and away from any significant density until the 401, where the station there is away from the major intersecting east-west municipal arterial road (Sheppard) and not well integated into the local rapid transit line.
From there, opportunities exist at Richmond Hill Centre (Langstaff) and maybe Major Mack (Richmond Hill). Otherwise, the two stations extending to the north are in a rural greenbelt abyss. Why prioritize that over at least two north running lines that intersect established settlements in the greenbelt to the west (Barrie: King City, Aurora, Newmarket, Bradford West Gwillimbury, Barrie) and east (Stouffville: Stouffville and Uxbridge), let along the Milton and Kitchener lines intersecting even bigger muncipalities?