Because the College car was a very different route. Royce Loop (Lansdowne & Royce) to Lipton Loop (Pape & Danforth) via Lansdowne, College, McCaul, Dundas, Broadview, Gerrard, Carlaw & Pape.
The old Harbord Car was on Harbord for a short distance as well. It had a very funny route. Until 1947, the route was Royce Loop to Lipton Loop via Lansdowne, Lappin, Dufferin, Hallam, Ossington, Harbord, Spadina, Dundas, Broadview, Gerrard, Carlaw, Riverdale, Pape. The portion from Dundas/Bay area east was a replacement of the College Car which was abandoned, replaced by Harbord and a through Lansdowne Car in the 1930s.
After 1947, the route was simplified and replaced part of the Dovercourt Car from Townsley Loop via Old Weston Road, Davenport, Dovercourt, Bloor, and onto Ossington to Harbord and eastbound. (The route is doable today, but requires 6 transfers via the 127, 161, 94, 510, 505, 506 and 72) The Dundas Car only went as far east as City Hall until the 1960s.