Where were your parents going?
Your last point is the one I find the most puzzling. You state the obvious -- this is a service designed to get someone from Pearson to Union, or vice versa. If you're grabbing the train to Niagara/Kingston or the GO to Hamilton/Oshawa, it might or might not be better to grab a bus or taxi from Pearson. If you're going to a hotel at Bloor & Avenue Road, you might make the switch at Bloor. But, those are not the core demographic. The core demographic is 'folks going to downtown Toronto.'