I think you inadvertantly answered your question without knowing it when you said why doesn't Vancouver have the layered approach
"...that bigger cities have...."
The mentality here is that of an adolescent city with an insular mentality tripping over itself as it grows up. The city council doesn't think "big city," not yet anyway.
If they did, they'd go look to other cities for examples, but they don't seem to. Brisbane, Australia has a commuter rail system and a subway downtown. Melbourne had an extensive commuter rail system when it was the size than Vancouver is now, and has an extensive subway system which includes the famous "Loop" (giving credit where it's due, Melbourne is twice the size of Vancouver)
Their transport system is one of the best in the world, and is very "layered," as are those of many cities, yet we don't seem to learn from others, which is a shame, and a mistake.